The Saucer vapor cap's larger size and saucer-like shape partially shield the hot metal parts, providing an extra layer of protection compared to our other caps. It is otherwise identical to those caps and can be used on all our pipe stems and WPAs. The cap must be modified to be used on the Vaporscope stem. We will do that if you order this cap and the Vaporscope stem in one order. If you are ordering a Saucer cap to go with a Vaporscope stem that you have, please note that in the comment section and we will modify the cap to fit.