Thomas Major Service Kit. Kit includes second stage C85487-P ring service kit, C85488-P valve assembly kit, C87079-P .50" stroke piston & rod assembly. Kit is compatible with standard Thomas models TA-4172, GH-417B (2ND STAGE) (This item currently has a tariff surcharge which will be added to your order as a separate line item. Tariff surcharges are subject to change.)