Thomas Service Kit. Kit includes 2 ea: Pump Heads w/Valves, Diaphragms, Diaphragm Rings, Diaphragm nuts, Diaphragm washers. Kit is compatible with standard Thomas YP-6, YP-15, YP-20 models (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.)