This is a Package of 12 Pairs of E-Z Mate® Magnetically Operated Center Shank-Medium Knuckle Couplers from Bachmann. FEATURES: E-Z Mate® couplers operate with a standard metal "glad hand" and under-track magnet. Compatible with all magnetically operated knuckle couplers. Easy to install! Coil metal springs. These couplers are center shank-medium. INCLUDES: 12 Pairs of Couplers REQUIRES: Under-Track Magnet (BACU6684) SPECS: Scale: HO (1:87) sdw 1/25/01 ir/jl kr8/15/06