Diameter: 13.5"Dual block design for use with Quartz or Daylite Lightbanks.Also fits the following lights:Arrisun 12 Plus 1200W Single Ended ParArri Studio 2K FresnelArri Compact 2500W HMI FresnelMole Baby Senior 5K Fresnel (4191)Mole 4K HMI Par (6491)Mole 2.5 / 4K Daylite Par (6641)Mole 5K Tungsten Par (6741)Cinemills Single Ended 2500W Par and 4K Par.