This sleeve of o-rings is from Symmons Industries, model number TT-15-400. It is for the TempControl Thermostatic Mixing Valve Cartridge 7-400NW by Symmons. (Equiparts part #53877). Comes with three (3) O-Rings.
EC Part Number: #58159
Manufacturer Number: TT-15-400
Manufacturer: Symmons Industries