The Perimeter Seal system is the latest technology from Racing Optics which allows for a tighter seal to the visor, blocking out dirt, dust, and water from behind the tearoff stack. The laminated technology creates a distortion-free optical lens. The XStack™ is a stack of 10 laminated tearoffs that are each 2mm thick. Each package contains 3 stacks of 10 tearoffs for a total of 30 tearoffs. Compatible with the GTX3 Carbon, GTX3, GP3 Carbon, GP3 Sport, GT5 Carbon, GT5, and HP5.