What Size Lock Works w/ the Cast Trailer Coupler e88FV?

Updated 11/12/2025 | Published 11/02/2025

Products Featured in This Question

Cast Trailer Coupler - Adjustable Channel Mount - Rotating Latch - 2-5/16" Ball - 21K

(6)

$79.32

InfiniteRule Lock for Cast Demco eZ-Latch Trailer Couplers - 2" and 2-5/16"

(147)

$67.95

Question:

The hole that a lock pin goes through is really small. Too small for the common Masterlock latch lock. Any idea what lock would work with this when it is attached to my truck?

asked by: Jamie A

Expert Reply:

Hey Jamie. The Cast Trailer Coupler item # e88FV uses a 5/16" pin to secure it so it requires a 1/4" pin diameter lock like the InfiniteRule Lock for Cast Demco eZ-Latch Trailer Couplers item # IR66FR. The fixed locking point on the coupler may need to be slightly drilled out to widen it.

What kind of trailer do you have?

expert reply by: Jerred H

InfiniteRule Lock
(click to enlarge)

Jamie A.

11/6/2025

Yes that is the lock I came up with as well, but I know it is designed for a different coupler so I was not sure. This must be a new design coupler. I have a Down2Earth 20ft car hauler 5 ton. Thanks for your response!

Jerred H.

11/6/2025

@JamieA You're welcome! You are correct the item # e88FV is newer. It's about a year old. It's an update on a Ram coupler that had the same knob but no locking hole for it. The InfiniteRule Lock item # IR66FR is our best solution for it. That's a nice trailer!

Jamie A.

11/10/2025

Hey Jared, I received the lock and it will fit through the hole on the knob, but not the stationary hole. I'm just going to drill it out as I assume no lock will fit at this point. Huge oversight with the coupler.

Jerred H.

11/12/2025

@JamieA Thanks for letting me know. I'll get that information updated. Sorry you had to modify the coupler but glad you found a way to make it work.