Thomas Major Service Kit. Kit includes C85485-P valve assembly service kit, C87053-P Teflon .804" stroke piston & rod assembly kit, C87860-P ring service kit. Kit is compatible with standard Thomas models TA-6052, GH-605B, GH-617B, GH-5VB, and first stage of TA-6172 & GH-617B models. Kit content services one cylinder. Depending on type of unit being serviced, you may need one or two kits.