These are Sets of E-Z Mate® Mark II Under Shank Medium Magnetic Knuckle Couplers by Bachmann®. Suitable for Ages 8 & Older. FEATURES: Created using precision molding techniques, the unique spring retention system securely holds the metal coil springs in place, making couple installation quick and easy for novice & experienced hobbyists alike Magnetically operated, & are compatible with all magnetically operated knuckle couplers currently on the market. Patent pending spring retainers. Fits most HO scale locomotives & rolling stock with built-in coupler pockets. Individually packaged and bar coded (2 couplers per package). Installation instructions provided on each package unit. INCLUDES: (12) Pairs SPECS: Scale: HO 1:87 kr10/13/04 ir/jxs