Master Lock - (3) Keyed Alike Trailer & Multi Purpose Padlocks, 37KA-3 This listing is for THREE (3) padlocks keyed alike (same key unlocks all) and six keys. The lock is also available with Bump Stop Technology. Search 37NKA in our storefront. If you order two 3-packs they will automatically be keyed the same. APPLICATION: Ideal for outdoor applications when needing many locks that utilize ONLY one key. The 37 lock works on 1-7/8 & 2 inch couplers & on virtually all standard hasp applications. These locks have a removable shackle sleeve. Sleeve off - Secures coupler latches. Sleeve on - Works best with hasps. TO FIT COUPLER LATCH: Remove the shackle sleeve. Shackle fits standard opening of 9/32" (7mm). Note that non-rigid shackle has enough play to fit virtually all coupler latches less than 7/8 wide. IMPORTANT NOTE: If using this style lock on a trailers coupler latch please be aware it is NOT recommended for all 2-5/16 couplers. It will fit some 2-5/16 couplers, the exception being 2-5/16 couplers that have the latch partially recessed from the top surface of the coupler, or latches that are wider than 7/8. SPECIFICATIONS: 3/4" (19mm) Armored Shackle Guard helps block bolt cutters. Revolving, case-hardened steel shackle sleeve resists cutting and sawing.