Better than electrical tape by far!
Used this on vehicles (starters) and trailer lights. Easy to use, looks like a professional fitting, and seems to hold tight.
Verified Buyer · Verified Purchase★ Verified
3:1 Dual Wall · 10ft Short Pack
5/16"
3:1 Heat Shrink
Fits8–10 AWG8mm
5/16 inch heat shrink tubing fits 8–10 AWG wire — winch feeds, solar charge-controller output, LiFePO4 interconnects, and high-current accessory runs. ABYC E-11 Table XI rates 10 AWG at 30A and 8 AWG at 40A bundled, currents at which a corroded crimp becomes a hot joint rather than an open circuit. At 8mm expanded, the tube clears bare 8 and 10 AWG conductors and recovers to roughly 2.7mm. It also covers the ring terminals and small lug barrels common on 10 AWG, which measure 7–8mm across — measure the barrel, not the wire, and leave 20% clearance so the tube slides on without dragging. The adhesive liner flows at 120°C and seals the barrel throat where water normally enters. UL 224 rated, 600V. The 10ft pack suits a solar or 12V install that needs this size at only a handful of terminations.
★★★★★4.7 · 225 verified ratings across the Helixal range
13 in stock · Ships in 24h
Order up to 13 online · need more? Trade pricing
Size5/16" · 8mm
Click any size to navigate · 10 ft per roll
$8.8910 ft spool
→ Dispatched within 24 hours — delivered in 1–3 days→ 30-day money-back guarantee — 30 days to return it
Qty
1
Secured by Stripe · No account needed
→Ships USA & Canada
→ISO 9001
→Ships 24h
SKU: B0FJNM3K57 · 5/16" (8mm) · 10 ft
Spec Sheet
5/16"
data sheet.
Full industrial dual-wall adhesive spec in a convenient 10ft pack. Same 600V rated, waterproof polyolefin construction as the large bulk rolls.
Imperial Size
5/16"
Expanded diameter
Metric Size
8mm
Nominal
Roll Length
10 ft
Per spool
Wire Gauge
8–10 AWG
Bare conductor
Shrink Ratio
3:1
Dual wall
Construction
Dual Wall
Adhesive inner liner
Inner Layer
Hot Melt Adhesive
Waterproof seal
Voltage Rating
600V AC
UL 224 — 600 V rms
Temp Rating
-55°C to +125°C
Continuous service
Shrink Temp
100°C (212°F)
Shrinking starts
Adhesive Flow
120°C (248°F)
Keep heating until it shows
Material
Polyolefin
Outer sleeve
Flammability
Self-extinguishing
UL 224 Recognized
Color
Black
Standard finish
Standards
UL 224 Recognized
UL file E361230 · RoHS
UV Resistance
Yes
Outdoor safe
Waterproof
Yes — adhesive seal
360° coverage
Sizing over a connector? The Wire Gauge row above is for bare conductor. Heat shrink must be sized to the widest point it passes over, so a crimped butt splice or lug barrel needs a larger tube than the wire alone — a 22–18 AWG splice barrel measures 5–6mm, a 16–14 AWG barrel 7–8mm, and a 12–10 AWG barrel 9–11mm. Measure the barrel, allow about 20% clearance, and confirm the recovered diameter is smaller than the narrowest thing the tube must grip. Use the size calculator.
What the
trade says.
Verified Buyers ★ · Full Range4.7★★★★★225 ratings · 84% 5-starCombined verified-buyer rating for every Helixal product — all ratios, all sizes — not this size alone.
Good quality and sealing heat shrink
Heat shrink works good. Makes a nice sealed wire connection. Better than pre-cut heat shrink — you can make whatever length you want.
R Davis · Verified Purchase★ Verified
Smart format for repair work
Great for keeping several sizes on hand without the bulk. Same quality as the large rolls — the adhesive seals perfectly every time.
Travis M. · Verified Purchase★ Verified
Customer Reviews
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Sizing & Application — 5/16 inch, 10ft pack
A solar install needs this size six times. A bulk roll would outlive the array.
5/16 inch (8mm) fits bare 8–10 AWG and covers the ring terminals and small lug barrels used on 10 AWG, which measure 7–8mm. ABYC E-11 Table XI rates 10 AWG at 30A and 8 AWG at 40A bundled — charge-controller output, LiFePO4 interconnects, winch feeds. What makes it a short-pack size is not how rarely it is needed but how few times it is needed per system.
Counting the terminations on a real installation
Take a typical 12V house system: an array feeding a charge controller, the controller feeding a battery bank, the bank feeding a busbar and an inverter. The 8–10 AWG runs in that system are the controller output and one or two accessory feeds. Each has two ends, and each end takes about 4 inches of tube.
That is six to eight terminations, or roughly two and a half feet. A ten-foot pack covers the install with enough left for the service visits that follow. A 60ft roll covers the same install and then sits in a cupboard for a decade, because the next system will use different gauges in different places.
The seal matters at every one of those terminations, which is why the pack is dual wall rather than single. Water reaching the barrel throat of a charge-controller lug runs straight onto bare copper under the crimp. At 30 to 40 amps the resulting resistance shows up as a hot terminal on a thermal check, not as a dead circuit — and by then the cable behind it has corroded too.
5/16 inch short pack at a glance
| Property | Figure | Why it matters |
|---|---|---|
| Expanded diameter | 8mm (5/16") | Clears the 7–8mm ring terminals used on 10 AWG |
| Recovered diameter | ≈2.7mm | Grips bare 8–10 AWG and the jacket behind a terminal |
| Bare wire range | 8–10 AWG | 30A for 10 AWG, 40A for 8 AWG bundled (ABYC E-11 Table XI) |
| Typical 12V system uses | 6–8 terminations, ≈2.5 ft | One pack covers the install and the follow-up visits |
| Wall type | 3:1 dual wall, hot-melt lined | Seals the barrel throat where water reaches the crimp |
| Bulk equivalent | 60 ft roll | Twenty systems — stock for an installer, not an owner |
Measure across the terminal barrel at its widest, including any inspection window. Allow about 20% clearance so the tube slides on cold.
When to change size or format
01 · You install systems for a living
At several arrays a month the 60ft roll is the right purchase. The pack is sized for one system and its maintenance.
02 · The tube drags going on
Step up to the 3/8 inch pack. A tube forced on cold arrives pre-stretched, finishes looser than rated, and traps air at the shoulder.
03 · It is a lug, not a ring terminal
Lug palms on 8 AWG and up are much wider than the barrel. Measure the palm — that usually lands on the 1/2 inch or 5/8 inch pack.
04 · Above 600V
Our rating is 600V rms. On a 1000 Vdc PV array the conductor carries the rating (UL 4703, RHW-2/USE-2) and tubing seals the termination.
Keep reading →Heat Shrink for Solar PV Wiring · Summer Solar Install Guide · 5/16" 3:1 Dual Wall — 60ft bulk roll
How it shrinks.
01
Measure & Select
Verify the expanded diameter is 20–30% larger than your wire or connector. The tubing must slide freely before heat is applied — if it drags, go one size up.
02
Cut & Thread
Cut to length and thread onto the wire or cable before making the splice or crimp. Overlap each terminal or connector end by at least 10mm for a proper seal.
03
Apply Heat
The tubing starts shrinking at 100°C, but the adhesive liner only flows at 120°C — so keep the heat gun moving past the point where it looks shrunk. Start at the center and work outward to push air toward the ends. Adhesive will appear at the tube ends — that is your visual seal indicator.
04
Inspect
The tubing should be tight and uniform with adhesive visible at both ends. No gaps, lifting, or cold spots. Pull-test the finished connection to confirm the adhesive bond.
Watch
All Videos →See 5/16" In Use
Size ReferenceExpanded vs.
Expanded vs.
recovered.
Actual 5/16" tube at full expanded diameter (8mm) and after heat recovery. Use this as your fit reference before cutting.
Expanded: 8mm — slides over 8–10 AWG
Shrink ratio: 3:1 on full heat
Use it on.
01
Try Before You Buy Bulk
Order a 10ft pack to verify the size fits your connector before committing to a large roll. Test fit, shrink one piece, then buy the bulk roll with confidence.
02
Field Repair Kits
Keep a set of short rolls on the service van or boat. Enough for any repair job without hauling large rolls — one 10ft roll handles most splices.
03
Stock Multiple Sizes Cheap
For the same cost as one large roll, stock several different sizes in short packs. Covers more connector diameters for the same investment.
04
Marine & Outdoor Spot Repairs
Seals individual connections on boat wiring, outdoor electrical, and trailer harnesses. Same waterproof adhesive seal as the large rolls — just 10ft.
05
Low-Volume Production
Ideal for small-batch cable assembly and prototype builds where a full bulk roll would sit unused. Cost-effective for runs of fewer than 50 connections.
06
One-Off Automotive Builds
Custom automotive and motorcycle builds often need several sizes in small quantities. Short rolls let you match every connection without leftover material.
Size Guide
5/16" Questions.
Technical Guides
All Guides →From the Blog
Free Tool
Heat Shrink Size Calculator
Read Guide →Ratios2:1 vs 3:1 vs 4:1 Heat Shrink Ratio Guide
Read Guide →Complete GuideHeat Shrink Tubing: The Complete Guide
Read Guide →SizingSize Chart & Selection Guide
Read Guide →How-ToHeat Shrink for Battery Terminals
Read Guide →AutomotiveAutomotive Wire Protection Guide
Read Guide →Also available — 5/16" in other lines
All 13 sizes.
View line overview →3/32"2.4mm10 ft1/8"3.2mm10 ft3/16"4.8mm10 ft1/4"6.4mm10 ft
Current5/16"8mm10 ft
3/8"9.5mm10 ft1/2"12.7mm10 ft5/8"16mm10 ft3/4"19.1mm10 ft1"25.4mm10 ft1-1/4"31mm10 ft1-1/2"38mm10 ft2"50.8mm10 ftRecovered diameter is approx. 1/3 of the expanded size shown · All sizes ship to USA & Canada