Below are two images that show the differences between a XS Scuba Pro Valve and a Thermo Pro Valve.

For the most part the two valves are identical. The XS Scuba Pro Valve above uses a bonnet o-ring. Various websites indicate that the bonnet o-ring size is a Viton 015 which is incorrect. While the o-ring fits, it doesn't seal the valve correctly and will leak once pressurized.

The Thermo Pro Valve instead uses a copper crush washer (not shown) to seal the valve assembly. Also not shown is the teflon packing that goes in-between the hand wheel and bonnet nut. Valve service is easy and straight forward. The plug and seat assembly, teflon packing, stem o-ring (Viton 010), and inlet o-ring (Viton 214) are universal between valves. The remaining parts are cleaned and reused.

Seattle, WA.