12 Couplings and transmission components in the nature of drive shafts, power take-off drive shafts, joints, clutches, and gearboxes for land vehicles; couplings for land vehicles; replacement parts for all the aforesaid goods; connecting pieces, namely, attachment and locking elements for use with couplings for land vehicles, other than parts of motors and engines; trailer hitches for vehicles, namely, tractors and utility vehicles; attachment devices, namely, hitches, and their parts for tractors and utility vehicles; trailers for vehicles, namely, tractors; tractor parts, namely, trailing hitch locking mechanisms and hold-down clamps sold as a unit therefor for attaching agricultural implements to tractors; vehicle parts, namely, drive shafts, universal joint shafts being couplings, double joint shafts being couplings, cardan shafts being couplings, universal joints, joint forks being parts of couplings, constant velocity joints, universal cardan joints, universal joints, and universal joint yokes being parts of couplings, all the aforesaid goods for land vehicles, and replacement parts therefor; drive shafts and transmission shafts for land vehicles; clutches and components, namely, houses, hubs, yokes, bearings, cams, and thrust plates, and replacement parts therefor for land vehicles; drive shafts, engine mounts, and thrust bearings for boats; universal joint shafts being couplings for power transmission, joints being couplings for power transmission, couplings, overload couplings, and freewheel couplings, and gearboxes, all for tractors, and replacement parts therefor; couplers in the nature of trailer hitches for connecting tractors to machine-driven agricultural implements or non-mechanically driven agricultural implements and integral components sold as a unit and replacement parts therefor, namely, coupling frames, lower links, upper links, coupling hooks, lateral struts, lateral stabilizers, spacers, lifting struts, and ball guide cones; universal joint shaft couplers for connecting tractors and machine-driven agricultural implements; protective devices for covering the rotatable parts of universal joint shafts, gearboxes, and couplings for tractors, namely, guard tubes, protective covers, guard cones, and safety shields; drives and spare parts thereof for tractors, self-propelling work machines, and self-propelling agricultural and construction machines; hydraulic pumps, hydraulic cylinders, hydraulic valves, and hydraulic engines for tractors, self-propelling work machines, and self-propelling agricultural and construction machines; electric drives for tractors; engines for tractors; hydraulic engines for tractors