The #149 is interchangeable with the #29 and most manufacturer's Medium Underset OEM knuckle couplers. For a #39 equivalent use the #149 in a #252 Gearbox.
Package Includes:
It is not recommended to use a metal coupler directly on a metal surface or in a metal draft gearbox to avoid possible electrical crossover and shorting that may cause damage. Use the provided insulated gearbox or insulated #29 coupler.