Guide
Shrink ratio: what 2:1, 3:1, 4:1 and 5:1 actually buy you
5:1 is the widest ratio published in this range and it costs 5.0 mm of recovered wall. Size against the largest obstruction the tube must pass, divided by the smallest diameter it must close onto.
This is the network's single shrink-ratio page; the sibling reference sites link here rather than restate it. Every figure below is read off the manufacturer's own selection charts.
Two diameters decide the job. The largest obstruction on the run — a crimp, a lug palm, a back shell, a joint shell — sets the supplied ID. The smallest diameter the tube must close onto sets the recovered ID. Ratio is only the span between them, and it is the last thing you pick, not the first. No series here is published above 5:1; past that the answer is a moulded shape.
The definition is arithmetic. A 3:1 tube recovers to a third of its supplied diameter, a 2:1 tube to half. Both ends are qualified on the chart: supplied ID is published as a minimum, recovered ID as a maximum. The GDW sheet spells the symbols out — D is diameter as supplied, d is diameter as free recovered, T is free recovered wall thickness. Free means nothing inside the tube. A tube cannot recover past the object it is sitting on, so the recovered column is a ceiling on travel, not a description of your finished joint.
The four terms the charts use
- Supplied ID (D)
- Internal diameter as delivered, published as a minimum on the GLC, GSC, GMW, GHW and GMW 5x charts. The tube will pass an obstruction at least this wide.
- Recovered ID (d)
- Internal diameter after free recovery, published as a maximum. The smallest the tube goes with nothing inside it.
- Recovered wall (T)
- Wall thickness at free recovery. The tolerance is not one convention: ±10% on GLC, GMW, GHW and GMW 5x; an absolute ±0.10 to ±0.20 mm on GSC 3X; positive-only, +0.10 to +0.20 mm, on GLC3; a bare minimum on the GDWH harness sleeve; and none printed at all on the GDW dual-wall charts or the GSC thin-wall chart.
- Shrink ratio
- D divided by d, rounded to a family label. Do the division yourself when the fit is close. GMW 10/3 sits in a 3:1 chart and divides to 3.3:1, GMW 425/120 to 3.5:1, GHW 12/3 to a clean 4:1, and GLC-SV 45/25 to 1.8:1 in a series sold as 2:1.
Five ways to reach 4.0 mm recovered
Three of these share a 12.0 mm supplied ID, so the only variables left are what the wall costs and whether the manufacturer will put a voltage class on it at all.
| Ratio | Part | Supplied ID | Recovered wall | Published insulation |
|---|---|---|---|---|
| 2:1 | GLC 8.0/4.0 | 8.0 mm | 0.56 mm | 3.3 kV |
| 3:1 | GSC 3X 12.0/4.0 | 12.0 mm | 0.75 ±0.15 mm | 3.3 kV |
| 3:1 | GLC3-12.0/4.0 | 12.0 mm | 0.75 +0.20 mm | 600 V |
| 3:1 | GDW 12/4 | 12.0 mm | 1.5 mm incl. adhesive | no voltage class published |
| 4:1 | GDW 16/4 | 16.0 mm | 1.8 mm incl. adhesive | no voltage class published |
Recovered wall by ratio band
| Ratio | Series | Range (supplied/recovered) | Recovered wall (mm) |
|---|---|---|---|
| 2:1 | GSC flame retardant | 1.0/0.5 to 100/50.0 | 0.28 to 1.27 |
| 2:1 | GLC thin wall | 6.0/3.0 to 100/50.0 | 0.56 to 1.27 |
| 2:1 | GLC-SV vented | 20/10 to 70/35 | 0.78 to 1.10 |
| 3:1 | GLC3 commercial | 1.5/0.5 to 39.0/13.0 | 0.45 to 1.15 |
| 3:1 | GSC 3X thin wall | 1.5/0.5 to 100.0/33.0 | 0.45 to 2.60 |
| 3:1 | GMW medium wall | 10/3 to 425/120 | 1.5 to 3.5 |
| 3:1 | GHW heavy wall | 12/3 to 425/120 | 2.4 to 4.5 |
| 3:1 | GDW dual wall | 3/1 to 50/17 | 0.9 to 2.4 incl. adhesive |
| 4:1 | GDW dual wall | 8/2 to 16/4 | 1.2 to 1.8 incl. adhesive |
| 5:1 | GMW 5x | 30/6 to 160/32 | 4.3 to 5.0 |
All walls are free-recovered figures. Two columns are not monotonic: on both the GLC and GSC charts 80.0/40.0 is 1.27 mm while the larger 100/50.0 is 1.17 mm, and GSC 3X steps from 1.50 mm at 39.0/13.0 to 2.50 mm at 50.0/16.0 — one size, two thirds more wall. Every row is expanded size by size on the size chart.
Which band the job is in
2:1, general insulation. GSC runs 1.0/0.5 to 100/50.0 and carries the thinnest wall published anywhere here, 0.28 mm, with flammability passed to UL 224 VW-1. GLC covers 6.0/3.0 to 100/50.0 on the same ratio. Both are published for insulation up to 3.3 kV. Use 2:1 wherever the tube can be threaded on before the end fitting goes down — 0.56 mm of wall against 4.3 mm on the 5:1 grade is the whole argument.
3:1, one obstruction to clear. Five series carry 3:1 and they are not interchangeable. GMW 10/3 to 425/120 insulates connectors on low-voltage terminations and straight-through joints to 3.3 kV; GHW 12/3 to 425/120 mechanically protects and outer-seals underground joints to 36 kV. Both conform to IEC 60684-3-247 and both shrink at 125°C to IEC 216. GDW 3/1 to 50/17 covers the same span when the gap also has to be sealed. In thin wall the series matters more than the label: GSC 3X 1.5/0.5 to 100.0/33.0 is published to 3.3 kV, GLC3-1.5/0.5 to 39.0/13.0 to 600 V. At 12.0/4.0 they are the same ratio and the same 0.75 mm wall, at under a fifth of the voltage.
4:1, a crimp mid-run. The published 4:1 chart is three rows: GDW 8/2, GDW 12/3, GDW 16/4, all adhesive-lined. That is the whole band. For a harness splice the manufacturer lists the GDWH sleeve at 4:1, GDWH-1 at 5.75 mm supplied through GDWH-5 at 18.30 mm; its chart carries an unlabelled last column, so read anything beyond the part code and D off the sheet itself. Above 16 mm supplied there is no 4:1 row and GDW reverts to its 3:1 chart.
5:1, a body and its cable. GMW 5x 30/6 to 160/32 is the only 5:1 series here, and the only one whose label is exact — every one of its eleven rows divides to precisely 5.0. It shrinks at the same 125°C as GMW and GHW and holds the same -40 to +110°C continuous limit, so nothing about the heat changes. What changes is mass: 4.3 to 5.0 mm of wall. Adhesive is an ordering option rather than a default, and the part number carries a position for it.
Two issues of the GDW chart do not agree
The standalone GDW dual-wall sheet publishes a 3:1 chart and a 4:1 chart, runs 3/1 to 50/17, and gives GDW 3/1 as 0.9 mm of recovered wall over 0.35 mm of adhesive. The thin-wall booklet publishes GDW as 3:1 only, runs it to 100/34, and gives the same GDW 3/1 as 1.0 mm over 0.4 mm with GDW 50/17 at 2.5 over 1.2. Same part codes, different walls, a different top size, and only one of the two offers 4:1 at all. This page quotes the standalone sheet. Confirm which issue you are holding before a 75 mm supplied size goes on a drawing.
The wall on a real substrate is not published
T is defined on the GDW sheet as free recovered wall thickness, and every wall column on the thin-wall, medium and heavy wall, dual-wall and GMW 5x charts is a free-recovery figure. None of them publishes a wall for a tube stopped part-way by the part inside it. If your recovered ID falls between two rows and the dielectric margin is tight, ask the manufacturer for the wall at your actual diameter rather than reading the free-recovery column as though it described your joint.
Ratio questions from the bench
Is a higher ratio simply a better tube?
Does the same size code mean the same ratio in every grade?
Why is 4:1 available in only three sizes?
Do the high-ratio grades need a hotter gun?
Can more ratio replace an adhesive lining?
Does ratio tell me anything about length?
Next, in order
- Size chart: supplied ID, recovered ID, recovered wallEvery series above, expanded row by row.
- Why the tube has a recovered size at allCrosslinking, expansion, and the memory that sets d.
- Installing: heat, distance and stroke orderWhere a 4.3 mm wall costs you time on site.
- Why a recovered tube failsUndersized recovery is the first of the five faults.
- GMW 5x at 5:1, in detail
- GMW and GHW, 3:1 from 10/3 to 425/120
- When the span is too wide for any tube
Send two diameters, not a part number
The largest obstruction the tube must pass and the smallest diameter it must close onto, both in millimetres, plus whether the run has to be sealed. Those three facts pick the band and the row.