First, refer them to our website or video to see the different types, if they still are not sure ask them:
Standard (Std)Glass- (our first design) Nothing is ground on the wand or heater cover. ——Heater cover has a small hole and the wand is fluted at the end and you have to hold it up to the heater cover.
Ground Glass- (also called conical) this is like the DBV glass.
Spherical Glass (SGG)-The wand is like a ball joint (this is our top of the line, larger bowl, never gets stuck and works with the Hands Free Attachment Glass Type Link http://silversurfervap.com/index.php/silversurfervap/info/faq.html#n