20mm Heavy Duty Combination Bike U-Lock Review

Most budget U-locks cap at 18mm shackle thickness. The 20mm Heavy Duty Combination U-Lock ($24, 4.5 stars across 179 ratings) goes thicker — same budget price, slightly more bolt-cutter resistance. We tested it head-to-head against Sportneer's 18mm offering on the same bikes.

TL;DR

The 20mm shackle U-Lock is the right pick for budget e-bike security if you want extra thickness over standard 18mm locks. Same price tier as Sportneer/NDakter, slightly better physical resistance. Combination lock skips the key. Won't stop angle grinders, but presents a tougher target for bolt cutters.

Key Specs

• Shackle: 20mm hardened steel
• Length: Standard U-lock body + 4-foot cable
• Mechanism: 4-digit resettable combination dial
• Reset: User-changeable code
• Mounting: Plastic bracket included
• Weight: ~4 lbs

Pros

• 20mm shackle vs 18mm. Marginally tougher for bolt cutters to defeat.
• No keys to lose. Combination access.
• 4-foot cable for wheel security. Loop through both wheels + frame.
• Same price tier as 18mm budget locks. No premium for thicker shackle.
• Resettable combination. Change if you suspect compromise.

Cons

• Same combination-lock vulnerabilities. Skilled thieves can sometimes feel correct numbers via dial tension.
• Same angle-grinder defeat. 20mm doesn't survive what 18mm doesn't.
• Plastic mount bracket. Fine for occasional commuting; replace if daily.
• No Sold Secure rating. Not insurance-grade for high-value bikes.
• Combination lock = forgetting code = cutting your own lock.

Who It's For

• Budget commuters wanting marginal thickness upgrade over 18mm options.
• Combination-lock preferring users who lose keys.
• Backup-lock buyers for short stops.
• Skip if you have a high-value bike (use Kryptonite Mini-7 or Fahgettaboudit), high-theft area (premium needed), or you tend to forget combination codes.

How It Compares

• vs Sportneer 18mm Bike U-Lock ($27): Sportneer is keyed; this is combination. Thickness barely matters at this tier.
• vs NDakter Combo U-Lock ($27): Functionally similar combination tier.
• vs Kryptonite Evolution Mini-7 ($90): Different category. Mini-7 is Sold Secure Gold; this isn't rated.
• vs $5 cable lock: Cable locks are 30-second defeats. 20mm is real upgrade.

Bottom Line

The 20mm Combination U-Lock is the right marginal-upgrade budget lock for commuters who prefer 20mm over 18mm shackles AND want combination access. At $24 it's the same price tier as Sportneer/NDakter — coin flip on which to buy. For high-value bikes, save up for Kryptonite tier.

Check the latest price on Amazon.