Grade index · GSC 1.0/0.5 to GHW 425/120

Heat shrink tubing: every wall grade and ratio in one index

Fifteen series between 0.5 mm and 120 mm recovered ID and between 0.28 mm and 7.5 mm recovered wall, sorted by what the tube has to close down onto.

Open the size chart

Three axes, and the order to fix them in

Fix wall class from the voltage and the mechanical duty. Fix ratio from how far the tube has to close. Fix lining last, from whether the joint has to stay dry. Nothing else in the range is a variable.

Thin wall recovers at 0.28 mm to 1.27 mm and is rated to 3.3 kV at most. Medium wall, GMW, recovers at 1.5 mm to 3.5 mm and insulates connectors on low-voltage terminations and straight-through joints to 3.3 kV. Heavy wall, GHW, recovers at 2.4 mm to 4.5 mm and is the mechanical protection and outer seal on a buried joint to 36 kV. Both conform to IEC 60684-3-247.

Ratio decides how much of one part number's range you can spend. 2:1 on GSC, GLC and the vented GLC-SV. 3:1 on GLC3, GSC 3X, GMW, GHW and the main GDW chart. 4:1 on the second GDW chart and on the GDWH harness grade. 5:1 on GMW 5x, which takes 160 mm supplied down to 32 mm recovered in a single size. Ratio is worked through at shrink ratio explained.

Bare tube insulates and nothing more. Hot-melt adhesive seals: GDW and GDWH carry it as standard, GMWR and GHWR are co-extruded with it, and GMW, GHW and GMW 5x list it as an option against IP68. Semi-conductive lining does neither job. It grades a field, and it belongs inside a joint.

GDLT, semi-conductive GCT and anti-tracking GAT are for the inside of an MV joint and the surface of an outdoor termination, to 36 kV. They are not general insulation. On the same 30 mm supplied ID, GDLT 30/11 recovers to a 5.0 mm wall where GLC 30.0/15.0 recovers to 0.87 mm, and the GDLT leaves a semi-conductive surface where a control cable wants none.

This index covers extruded tube. Moulded boots, breakouts, shrouds, end caps and jointing kits are a different geometry, indexed by the same publisher at cablebreakoutboots.com; the point at which a tube stops being the right answer is set out at tube or moulded shape. One extruded grade has no page here: GRT red insulation tube, for build-up insulation inside MV power cable joints, published in standard, heavy wall and extra heavy wall charts. Its listing is the manufacturer's.

Fifteen series, one row each

Read the recovered ID column first. That is the number the job hands you; supplied ID only says what the tube will pass over on the way there. Every row here is expanded size by size on the size chart.

Series	Supplied ID (mm)	Recovered ID (mm)	Recovered wall (mm)	Ratio	What it is for
GSC · GSC/YG	1.0–100.0	0.5–50.0	0.28–1.27	2:1	Flame-retardant thin wall: harnessing, in-line components, colour coding, yellow/green earth lead
GSC 3X	1.5–100.0	0.5–33.0	0.45–2.60	3:1	The 3:1 thin wall that keeps the 3.3 kV rating and the VW-1 flame test
GLC	6.0–100.0	3.0–50.0	0.56–1.27	2:1	Plain black thin wall to 3.3 kV: light harnessing and switchgear connections
GLC3	1.5–39.0	0.5–13.0	0.45–1.15	3:1	Commercial-grade thin wall to 600 V, specified for tunnels and mines
GLC-SV	20.0–70.0	10.0–35.0	0.78–1.10	2:1	Vented thin wall: recovers wrinkle-free over bends and threaded fasteners without grease
GMW	10–425	3–120	1.5–3.5	3:1	Medium wall: connector insulation on LV terminations and straight joints to 3.3 kV
GHW	12–425	3–120	2.4–4.5	3:1	Heavy wall: mechanical protection and outer seal on underground joints to 36 kV
GMWR	12–130	3–36	1.5–3.0	Co-extruded, high ratio	Adhesive-lined medium wall: waterproof sealing on terminations, joints, pipes and pipe connections
GHWR	12–140	3–42	2.2–4.2	Co-extruded, high ratio	Adhesive-lined heavy wall: CATV and CCTV plant, control-cable splicing joints
GMW 5x	30–160	6–32	4.3–5.0	5:1	One size across a connector, its back shell and the cable behind it
GDW	3.0–50.0	1.0–17.0	0.9–2.4 including adhesive	3:1 and 4:1	Dual wall: splice and harness sealing where the adhesive, not the tube, is the seal
GDWH	5.75–18.30	1.25–4.35 wire, 2.65–7.40 splice	0.60–0.90 minimum	4:1	Harness dual wall: one part sealing over a crimped or welded splice and the wire either side
GDLT	30–120	11–45	5.0–7.5	Not stated	Double layer: insulating inner, semi-conductive outer, inside joints to 36 kV
GCT	30–180	10–55	Not published	Not stated	Semi-conductive screening over the built-up insulation on a connector, to 36 kV
GAT · GAT HW	Not published	Not published	Not published	Not stated	Anti-tracking surface for MV joints and terminations to 36 kV

Where the published record stops

Three cells above are blank for a reason. GAT and GAT HW are named as a normal-wall and a heavy-wall selection chart, but no GAT dimension appears on the manufacturer's page or in the datasheet text available to us. GCT is given as a range, GCT 30/10 through GCT 180/55, with no recovered wall against it. And no source states a shrink ratio for GDLT, GCT or GAT, so do not back-calculate one from D and d: recovered ID is a maximum, supplied ID a minimum, and the quotient is not the rating. Ask for all three in writing before a drawing quotes a size.

Six grades, six pages

Each grade below carries its full published chart on its own page. Pick on recovered ID first, then on the column that separates it from the grade next to it.

Five series at 2:1 and 3:1

Thin wall — GSC, GSC 3X, GLC, GLC3, GLC-SV

GSC 1.0/0.5 to 100/50.0 at 2:1 is the widest of the five charts, and GLC repeats it from 6.0/3.0 up in black only. Voltage separates the rest: GSC and GLC are rated 3.3 kV, GLC3 is 600 V, and GSC 3X is the only 3:1 thin wall that keeps 3.3 kV.

3:1 · 1.5 to 4.5 mm wall · to 36 kV

Medium and heavy wall — GMW, GHW

Both conform to IEC 60684-3-247 and both are carbon-black loaded against UV. GMW insulates connectors to 3.3 kV; GHW seals and mechanically protects a buried straight-through joint to 36 kV. Maximum cut length on either is 1200 mm. A flame-retardant sheet publishes its own chart, GMW 10/4-FR to 180/60-FR and GHW 12/5-FR to 180/60-FR: same supplied IDs, larger recovered IDs, so an FR substitution changes the fit.

0.35 to 0.9 mm recovered adhesive

Adhesive-lined — GDW, GDWH, GMWR, GHWR

Here the adhesive is the product. GDW co-extrudes polyolefin over hot-melt in nine sizes at 3:1 and three more at 4:1; GDWH takes the harness case at 4:1 with separate wire and splice diameters. GMWR and GHWR put the same lining under a medium or heavy wall for terminations, joints and pipework. The seal is the melt flowing round the connection, not the tube gripping it.

160 mm supplied to 32 mm recovered

5:1 — GMW 5x

Eleven sizes, GMW 5x 30/6 to 160/32, recovered wall 4.3 mm to 5.0 mm. Built for the step from a connector body down to the cable behind it. Adhesive is optional and takes it to IP68; the order code carries A for adhesive and U for none.

Inside an MV joint, to 36 kV

Screening — GDLT, GCT, GVOT

GDLT co-extrudes a 20 kV/mm insulating inner with a semi-conductive outer at 1 x 10³ Ohm.cm, in eight sizes from 30/11 to 120/45. GCT screens the built-up insulation over a connector, GCT 30/10 through GCT 180/55. GVOT carries an integrated varistor stress-control system in six sizes, 30/15 to 85/42, normally supplied as part of a termination rather than bought loose.

A surface problem, not a wall problem

Anti-tracking — GAT, GAT HW

Non-tracking cross-linked polyolefin for MV joints and terminations to 36 kV, halogen free, flame retardant and weather resistant, under Technical Qualification Report QR 1021. A normal-wall and a heavy-wall chart are both named; neither is printed.

Two issues of the thin-wall datasheet rate GSC differently

The sheet published as Heat-Shrink-Thin-Wall-Tubes.pdf rates GSC for electrical insulation up to 3.3 kV and cites UL 224 file E328193. A second issue rates the same series up to 600 volts and cites file E328538, which is the number in the company's own certification timeline. GLC's separate sheet says 3.3 kV. The charts differ as well: the second issue adds GSC 3.5/1.7, 9.0/4.5, 12.0/6.0, 22.0/11.0 and 76.0/38.0, drops 60.0/30.0, 70.0/35.0 and 80.0/40.0, which is where the 1.27 mm wall lives, and carries GDW out to 100/34 where the GDW sheet stops at 50/17. Specify against the issue you were actually sent, and have its date confirmed in writing before a panel drawing quotes a voltage.

Continuous temperature limit by grade

Grade	Continuous temperature limit	Test method
GSC · GSC/YG thin wall	-55 °C to +125 °C	IEC 216
GSC 3X thin wall, 3:1	-55 °C to +125 °C	IEC 216
GLC thin wall	-55 °C to +125 °C	IEC 216
GLC3 commercial thin wall	-55 °C to +125 °C	IEC 216
GLC-SV vented thin wall	-40 °C to +125 °C	IEC 216
GMW medium wall	-40 °C to +110 °C	IEC 216
GHW heavy wall	-40 °C to +110 °C	IEC 216
GMW 5x high ratio	-40 °C to +110 °C	IEC 216
GMWR · GHWR co-extruded, outer wall	-55 °C to +125 °C	IEC 216
GDW dual wall, outer wall	-55 °C to +125 °C	IEC 216
GDWH harness dual wall	-55 °C to +125 °C	IEC 216
GDLT double layer, both layers	-40 °C to +100 °C	IEC 216

Each figure is taken from that grade's own datasheet rather than averaged across the family, because the spread is 15 °C at the cold end and 25 °C at the hot end. Shrink temperature is published only for the heavier families: 125 °C for GMW, GHW and GMW 5x, and 135 °C for GDLT, whose sheet also gives 100 °C minimum shrink and 130 °C minimum full shrink.

The rest of the reference

Four pages that change the answer, and three that send you somewhere else.

Questions this index gets asked

GLC or GSC — they look like the same chart?

From 6.0/3.0 upward they are the same chart: identical supplied and recovered IDs, identical 0.56 mm to 1.27 mm walls, both 2:1. GSC adds the things a specification asks for. It is halogen free, flame retardant and self-extinguishing, tested to UL 224 VW-1 and MIL-I-23053/5 Class 2 and 3, and listed in seven standard colours, one of them the yellow/green earth stripe. GLC is black, and its datasheet carries no flammability row at all. Below 6.0 mm supplied ID the 2:1 chart is GSC only, down to GSC 1.0/0.5 at a 0.28 mm wall.

GLC3 or GSC 3X, if the job needs 3:1 in a thin wall?

GSC 3X, unless 600 V is genuinely the ceiling. The two charts share eight sizes, 1.5/0.5 through 39.0/13.0, with the same recovered wall on seven of them. What separates them is the rating: GLC3 is published for electrical insulation up to 600 volts, GSC 3X up to 3.3 kV, halogen free and flame retardant to UL 224 VW-1. GSC 3X also runs on to 100.0/33.0, and its wall at 39.0/13.0 is 1.50 mm against GLC3's 1.15 mm. GLC3 has a page on the manufacturer's site; GSC 3X is on its own datasheet, Issue 2, December 2025, so quote the sheet.

Which grades take a hot-melt adhesive lining?

GDW has it as standard, 0.35 mm to 0.9 mm of recovered adhesive beneath a 0.9 mm to 2.4 mm total wall, and GDWH does the same over a harness splice. GMWR and GHWR are co-extruded with it. GMW, GHW and GMW 5x list it as an option, tied to IP68, and the order code is where you say so: GMWR 12/3 A 1000 is the 12/3 size with adhesive at 1000 mm cut length, and GMW 5x 30/6 U 1000 is the same construction without. The flame-retardant medium and heavy wall sheet puts FR in that same slot.

Does one 5:1 tube replace two 3:1 sizes?

On the published charts, yes. GMW 5x 160/32 recovers to 32 mm, while the 3:1 chart's 160 mm size, GMW 160/50, stops at 50 mm, so the last 18 mm of the step needs a second part. What you pay is wall: 4.3 mm to 5.0 mm recovered against 1.5 mm to 3.5 mm on GMW. The continuous temperature limit is identical at -40 °C to +110 °C, so the choice is stock-holding and recovery, not thermal.

Can a thin wall tube be used at 11 kV if it is doubled up?

No. The published ratings are 3.3 kV on GSC, GSC 3X and GLC and 600 V on GLC3, and no thin-wall grade in this range is rated above 3.3 kV at any thickness. Above 3.3 kV the answer is GHW to 36 kV, and inside an MV joint it is the screening and anti-tracking grades.

Send the recovered ID, not the part number

Four numbers settle the grade in one reply: the diameter the tube must close down onto, the largest diameter it must pass over, the voltage, and whether the joint has to stay dry. Add the cut length if it matters, because 1200 mm is the ceiling on GMW and GHW.

Send the sizes Compare with cold shrink