SCBA Bottle Cap

This thing was made with Tinkercad.

(Where the hell's the picture?)
We use these to protect the threads of SCBA (firefighting air packs) bottles during storage and transport. They are a cheap little plastic cap that costs nothing. Would be fun to put someone's head or a skull on the cap. The plain white tapered cylinder is the internal dimensions of a Scott SCBA bottle cap - use it as a "hole" to make anything into an SCBA bottle cap. Different manufacturers may have different dimensions