It drives me crazy to order only one item from a vendor.
If you happen to need stuff from Spruce, the same Usher Cap "O"-ring is part number 05-02146.
RV-7A: Flying since April 15, 2012. 800 hrs
YIO-360-M1B, mags, CS, GRT EX and WS H1s & A/P, Navworx
Unpainted, polished....kinda'... Eyeballin' vinyl really hard.