Nice product at great price
Was wiring my car and had quite a few smaller wires to crimp and cover. This worked great — shrinks clean and consistent every time.
Church's · Verified Purchase★ Verified
2:1 Single Wall · UL 224 Recognized
5/16"
2:1 Heat Shrink
Fits8–10 AWG8mm
5/16 inch heat shrink tubing fits 8–10 AWG wire — the gauge used for high-current automotive feeds, LiFePO4 battery connection leads, solar charge controller output wiring, and winch solenoid circuits. ABYC E-11 Table XI rates 10 AWG at 30A and 8 AWG at 40A in a standard bundled installation; at these current levels, reliable connection integrity at each terminal crimp becomes essential to system performance. At 8mm expanded diameter, this tube slides freely over 8 and 10 AWG conductors and recovers to approximately 4.0mm. The 2:1 single-wall construction, qualified to UL 224, is well suited for dry indoor installations where insulation protection and compliance rating are the priority. For engine compartment runs, battery terminals exposed to rain, or any connection that will see regular moisture, the 3:1 dual-wall adhesive liner provides the sealed protection this size demands in outdoor and mobile environments. At 120 feet per roll, 12-volt shops and renewable energy installers working with LiFePO4 battery banks and inverter systems get enough material to complete full installations without mid-project re-orders.
★★★★★4.7 · 225 verified ratings across the Helixal range
30 in stock · Ships in 24h
Order up to 30 online · need more? Trade pricing
Size5/16" · 8mm
Click any size to navigate · 120 ft per roll
$21.59120 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: B0FJHXLNHL · 5/16" (8mm) · 120 ft
Spec Sheet
5/16"
data sheet.
High-volume UL 224 Recognized polyolefin at an honest per-foot cost. The industry standard for band marking, bundling, and dry indoor electrical insulation.
Imperial Size
5/16"
Expanded diameter
Metric Size
8mm
Nominal
Roll Length
120 ft
Per spool
Wire Gauge
8–10 AWG
Bare conductor
Shrink Ratio
2:1
Single wall
Construction
Single Wall
No adhesive liner
Adhesive Liner
None
Not waterproof
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
Material
Polyolefin
UL 224 Recognized
Certification
UL 224
Recognized Component
Flammability
Self-extinguishing
UL 224 Recognized
Color
Black
Standard finish
Moisture
Resistant — not sealed
Single wall only
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.
Perfect for bulk workshop use
Bought this for my automotive workshop and the 120ft roll is exactly what I needed. Shrinks consistently and cleanly every time. Much better value than small packs.
Mike R. · Verified Purchase★ Verified
Professional finish every time
Clean black finish, no bubbles or wrinkles when applied correctly. UL listing is important for commercial electrical work — ticks that box too.
James T. · Verified Purchase★ Verified
Customer Reviews
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Sizing & Application — 5/16 inch
If the tube drags going on, it has already failed. Do not force it.
5/16 inch (8mm) recovers to about 4mm and fits bare 8–10 AWG — winch feeds, solar charge-controller output, LiFePO4 interconnects. ABYC E-11 Table XI rates 10 AWG at 30A and 8 AWG at 40A bundled. It also covers the ring terminals and small lug barrels used on 10 AWG, which run 7–8mm across an 8mm bore. That is a tight clearance, and tight clearance is where the most common application error happens.
What forcing a tube on cold does to the finished joint
Heat shrink is manufactured by extruding tubing at its recovered size, cross-linking it, then expanding it while hot and freezing that expansion in. Heating releases the stored strain and the tube returns toward its original diameter. That is the whole mechanism, and it depends on the tube arriving at the joint in its as-supplied expanded state.
Push a tube over a barrel it barely clears and you stretch it further, cold, beyond what the process put in. That extra stretch does not recover — the tube comes down to its programmed diameter and no closer, so it finishes looser than the specification promises. Worse, the drag scrapes a ring of air ahead of the tube and traps it at the shoulder.
The result is a joint that looks correct and has a void at exactly the point that matters. Allow roughly 20% clearance over the widest measured point instead. If 5/16 inch drags over your terminal, the answer is 3/8 inch, not more force — and the small extra cost of the larger tube is trivially less than a return visit.
5/16 inch at a glance
| Property | Figure | Why it matters |
|---|---|---|
| Expanded diameter | 8mm (5/16") | Ring terminals on 10 AWG run 7–8mm — clearance is tight |
| Recovered diameter | ≈4mm | Grips bare 8–10 AWG and the jacket behind a terminal |
| Clearance to allow | ≈20% over the widest point | Below that, the tube stretches cold and finishes loose |
| Bare wire range | 8–10 AWG | 30A for 10 AWG, 40A for 8 AWG bundled (ABYC E-11 Table XI) |
| Wall type | Single-wall polyolefin | Insulation, abrasion resistance and strain relief in dry locations |
| Roll length | 120 ft | This size is used a few terminations per system; one roll outlasts several |
Measure across the barrel at its widest, including any inspection window. The wire gauge is not the sizing input on a terminated end.
When to step up or across
01 · The tube drags
Go to 3/8 inch. A tube that has to be worked on has already been stretched past its programmed recovery and will not close down as far as the datasheet says.
02 · The terminal sees weather
Solar and winch terminations are outdoor by definition. The 5/16" 3:1 Dual Wall seals the barrel throat where water enters; single-wall covers it without closing it.
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 1/2 inch or 5/8 inch.
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 →5/16" 3:1 Dual Wall — the sealed version · Heat Shrink for Solar PV Wiring · Summer Solar Install Guide
How it shrinks.
01
Measure & Select
Choose a size where the expanded diameter is 20–30% larger than your wire or bundle. Smaller tubes will slide on easier; slightly oversize is better than too tight.
02
Cut & Thread
Cut to length and thread onto the wire before making the splice. The tubing cannot pass over a crimped terminal — position it first, then complete the connection.
03
Apply Heat
The tubing starts shrinking at 100°C — use a heat gun and keep it moving until it has shrunk evenly along its length. Work from the center outward. Avoid open flame — it scorches the tubing and creates uneven shrink.
04
Inspect
Finished tubing should be tight with no bubbles or lifted edges. No adhesive will appear at the ends — this is single-wall tubing. Confirm even recovery across the full length.
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: 2:1 on full heat
Use it on.
01
Automotive Interior Wiring
Covers harness splices, stereo wiring, and interior electrical repairs in non-submerged locations inside the vehicle cabin.
02
Household Appliance Repair
Insulates wire splices and terminal connections on washing machines, dryers, and other appliances in dry indoor environments.
03
Workshop & Bench Wiring
Organizes and band-marks power tool wiring, extension cord repairs, and bench supply leads in garage and workshop environments.
04
Solar Wiring — Dry Locations
Covers solar panel wiring and charge controller connections on 12/24/48V DC systems in protected, non-submerged locations. On PV strings running above 600V the conductor must already be code-rated PV wire — heat shrink is the cover, never the primary insulation.
05
Harness Band Marking
Identifies circuits in large wire harnesses used in HVAC, industrial panels, and manufacturing equipment where conductors are routed indoors.
06
Terminal Insulation
Provides clean insulation sleeves over ring terminals, spade connectors, and butt splices in dry panel and enclosure environments.
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 →Uses2:1 Heat Shrink Uses — Bundling & More
Read Guide →SizingSize Chart & Selection Guide
Read Guide →ComparisonHeat Shrink vs Electrical Tape
Read Guide →Buyer's GuideBest Heat Shrink Tubing 2026
Read Guide →Also available — 5/16" in other lines
All 13 sizes.
View line overview →3/32"2.4mm120 ft1/8"3.2mm120 ft3/16"4.8mm120 ft1/4"6.4mm120 ft
Current5/16"8mm120 ft
3/8"9.5mm120 ft1/2"12.7mm120 ft5/8"16mm90 ft3/4"19.1mm90 ft1"25.4mm90 ft1-1/4"31mm60 ft1-1/2"38mm60 ft2"50.8mm60 ftRecovered diameter is approx. 1/2 of the expanded size shown · All sizes ship to USA & Canada