What Trailer Coupler Lock will Work with My Bulldog-style Bolt-On Coupler for 5,000 Pounds?

Updated 11/14/2025 | Published 10/16/2025

Products Featured in This Question

Master Lock 1-7/8", 2", and 2-5/16" Trailer Coupler Lock - Gray - Keyed Alike

(50)

$44.91

Master Lock Trailer Coupler Lock - 1-7/8", 2" and 2-5/16" Ball Couplers

(906)

$36.22

TowSmart Trailer Coupler Lock Kit - 1-7/8, 2, and 2-5/16 Couplers w/ Hitch Lock & Coupler Lock

(66)

$66.17

Question:

i am looking for a coupler lock that will work with this style coupler. i think this one will probably work ok, but i am wondering if there is a better one.

asked by: Rodger R

Picture of Trailer Coupler
(click to enlarge)

Expert Reply:

Hello Rodger,

There are a couple of different options for you. The one that you found, the Master Lock 1-7/8", 2", and 2-5/16" Trailer Coupler Lock - Gray - Keyed Alike # ML377KA, would work great. We have a similar style that also works: the Master Lock Trailer Coupler Lock - 1-7/8", 2", and 2-5/16" Ball Couplers # ML389DAT.

The kit that I use on my boat trailer when I am down at the lake is the TowSmart Trailer Coupler Lock Kit - 1-7/8", 2", and 2-5/16" Couplers w/ Hitch Lock & Coupler Lock # TS84FR. I really like this one because it uses the ball inside, and I clamp it down pretty tight. I have not had anyone take off with it yet!

I would say that the one you were looking at, the # ML377KA, would be the most difficult to try to remove.

What kind of trailer are you using this on?

expert reply by: Kate F

TowSmart Coupler Lock Kit
(click to enlarge)

Kate F.

11/13/2025

Hey Rodger, how did the Master Lock coupler lock end up working with your trailer? Your feedback could help others choose between that one and the TowSmart or the other Master Lock option. Sharing what you found might guide others looking for a secure fit.

Rodger R.

11/13/2025

@KateF The coupler lock works, but it is very loose. I think it will at least slow a thief down. The hitch pin lock for the truck receiver works just fine. The other two locks, to lock the hitch from being opened doesn't work at all. The range of fit on those locks is very tight and they won't work on either of my trailers. Thank you Rodger

Kate F.

11/14/2025

@RodgerR I am very sorry to hear that Rodger. I see that you did go with the # ML377KA, I am surprised to hear it is a lose fit. But you are right, it will definitely slow them down, usually makes them move onto something else that is not locked up. If people could just be decent humans, we wouldn't have to worry so much about keeping our stuff protected. I really do appreciate you taking the time to share your feedback =)