The Cylinder Dome with Marbles comes in your choice of 14mm or 18mm joint size. Having these sizes in a female joint gender means the glass dome can fit on most 14mm and 18mm dab rigs. The tall walls on the replacement dome protect your nail. The more narrow opening creates an easy tunnel that can be easily capped. Three marbles are located around the top of the dome. These raised bumps can really help with handling the Cylinder Dome with Marbles.