Bachmann HO Scale Flat-Back Wheelsets are replacements for wheels used on many Bachmann freight cars. Insulated wheelsets feature blackened-metal wheels and NMRA RP-25 profile for use on track with Code 70 and larger rail. 33′ wheels fit most freight cars and 36′ wheels are typically used on modern freight and most passenger cars. Flat-Back Wheelsets are part of the line of Bachmann HO Scale couplers and trucks.WARNING: This product can expose you to chemicals including Lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov