Master Lock 375DAT Class III/IV Snap-On Receiver Hitch Lock with 5/8-Inch Pin Trailer-hitch lock with 5/8-inch pin Locks boat trailers, utility trailers, camper trailers, and more onto hitch Precision tumbler mechanism resists picking; Class III/IV Sealed stainless steel body resists corrosion; solid brass cylinder cores and cases Fits 2-inch, square receiver tubes; accepts K1 key blank; limited lifetime warranty