Our plate and gasket pairs are available in 6″, 8″, 12″ and 20″. If you already own a cap system, including the clamps, this plate and gasket pair can be added to your toolbox. The 6″ & 8″ sets require 3 clamps, the 12″ set requires 4 clamps, and the 20″ set requires 5 clamps. Please order accordingly. Standard blowoff valve not included.