Trailer Ball Locks: How They Work and When to Use One
Our top picks
Master Lock 389DAT
Low price.
About $36 (masterlock.com list)
Check price at Master Lock ↗AMPLock BRP-2
Push-and-lock, no tools.
$129.99 (Strong) or $269.99 (Ultimate), amplock.com list
Check price at AMPLock ↗Master Lock 379ATPY
Low price.
About $36 (masterlock.com list)
Check price at Master Lock ↗
Comparison
| Lock | Best for | Fits | Price (approx.) | |
|---|---|---|---|---|
| Master Lock 389DAT | Best budget ball lock | Most 1-7/8 in, 2 in and 2-5/16 in couplers incl. surge-brake, rolled-lip, UFP | About $36 (masterlock.com list) | Check price ↗ |
| AMPLock BRP-2 (Ball Coupler Lock, Flat Lip) | Best custom-fit ball lock (flat lip) | 2 in and 2-5/16 in straight (flat) lip ball couplers | $129.99 (Strong) or $269.99 (Ultimate), amplock.com list | Check price ↗ |
| Master Lock 379ATPY | Universal alternative | 1-7/8 in, 2 in and most 2-5/16 in couplers | About $36 (masterlock.com list) | Check price ↗ |
How we chose: picks are based on published specifications, materials, fit charts, manufacturer information and patterns in owner reports. We have not lab-tested these locks. Prices are approximate list prices seen on maker sites in October 2026 and change often.
Our picks in detail
Master Lock 389DAT
Who it is for: Boat and utility trailers on a budget.
- Low price
- Wide fit incl. surge-brake couplers
- Bright red is a visible deterrent
- Cannot be keyed alike
- Universal fit leaves room to pry
- Type: Universal coupler (ball) lock
- Fits: Most 1-7/8 in, 2 in and 2-5/16 in couplers incl. surge-brake, rolled-lip, UFP
- Build: Red powder-coated steel, wafer tumbler, keyway cover
- Keyed alike: No (cannot be keyed alike)
- Price: About $36 (masterlock.com list)
Bright red as a visual deterrent.
Check price at Master Lock ↗AMPLock BRP-2 (Ball Coupler Lock, Flat Lip)
Who it is for: Owners of 2 in or 2-5/16 in flat-lip couplers who want a custom-fit ball lock.
- Push-and-lock, no tools
- Disc cylinder
- Two security levels and price points
- 5-year warranty with key registration
- Flat-lip couplers only
- Ultimate version is $269.99
- Type: Ball-style coupler lock (custom-fit)
- Fits: 2 in and 2-5/16 in straight (flat) lip ball couplers
- Build: Ductile iron and stainless steel, disc cylinder, push-and-lock; Ultimate (10 lb) and Strong (5 lb) levels
- Keyed alike: Yes (keyed alike across AMPLock products)
- Price: $129.99 (Strong) or $269.99 (Ultimate), amplock.com list
Fits flat-lip couplers only; check your coupler shape before ordering.
Check price at AMPLock ↗Master Lock 379ATPY
Who it is for: Budget buyers and people with several trailers.
- Low price
- Fits 1-7/8, 2 and most 2-5/16 in couplers
- Rekeyable commercial version
- Looser universal fit
- Lighter than custom steel locks
- Type: Universal coupler lock
- Fits: 1-7/8 in, 2 in and most 2-5/16 in couplers
- Build: Rust- and corrosion-resistant body, keyed different, rekeyable commercial version
- Keyed alike: Can be ordered keyed-alike commercially; retail is keyed different
- Price: About $36 (masterlock.com list)
Limited lifetime warranty.
Check price at Master Lock ↗This guide covers one angle
This page explains ball-style locks only: how they seat, which couplers they suit and their limits. For the full comparison of every option, see our hub guide: best trailer coupler locks.
How a ball lock works
The lock has a ball (or plug) that sits in the coupler socket and a clamp or shackle that locks around the coupler. While it is fitted, the coupler cannot latch onto a hitch ball, so the trailer cannot be towed by normal means.
Ball lock or full coupler lock?
Ball-style locks are light, cheap and universal. Their weakness is the exposed shackle or clamp, which can be cut. Full coupler locks enclose the coupler in steel, which takes longer to defeat. If your trailer sits unattended for days, a full lock is worth considering. More in our coupler lock guide.
How to choose
- Ball size: read the size stamped on your coupler (1-7/8 in, 2 in or 2-5/16 in). Custom-fit locks are sold per size; universal locks cover all three but fit looser.
- Coupler type: trigger latch, thumb latch, lever/latch style (Atwood-type), surge-brake (common on boat trailers) or cast-steel. Custom-fit makers publish fit charts; check yours before buying.
- Material and coverage: thick steel that wraps the whole coupler leaves less room for pry bars and cutters than a small ball plug with an exposed shackle.
- Lock cylinder: tubular and disc cylinders resist picking better than basic wafer locks. Look for a keyway cover so dirt and road salt stay out.
- Keyed alike: if you also lock the hitch pin, spare tire or doors, a keyed-alike set means one key for everything.
- Weather: powder coat, stainless pins and sealed keyholes matter if the trailer sits outside or near salt water.
Our pick
Master Lock 389DAT: best budget ball lock. Boat and utility trailers on a budget. If budget matters more, see the other picks above.
Check price at Master Lock ↗FAQs
- Will a trailer ball lock fit any coupler?
- Universal ball locks fit most 1-7/8, 2 and 2-5/16 in couplers, but unusual shapes (some surge brakes and cast couplers) may not fit. Check the maker's fit list.
- Is a red lock better?
- Bright colours like the red 389DAT are easier for a thief to spot, which can deter an attempt; security still depends on the lock itself.
- Can I tow with a ball lock in place?
- No. It must be removed before hitching.