Flat Top Quartz Banger w/ Opaque Bottom (Pick Joint Size)- 99.99% Pure SiO2 Opaque Quartz on Bottom- The opaque floor heats up much faster than traditional clear fused quartz, but can still hold heat well. The opaque surface is slightly textured which assists in the formation of nucleation sites at exceeding lower temperatures.- The beveled edge on the top of the nail creates a superior seal with your cap making the whole 'carb capping' process way more efficient.Specs:- Outer Diameter: 25mm- Bottom Opaque Thickness: 4mm- Side-Wall Thickness: 2.5mm- Recommended quartz insert size: 20mm (coming later this week)