Representing our first responders, the "Thin line" disks feature a blue contrasting line on the top of a Satin black disk. All of the "Thin line" disks feature a Diamond knurling pattern for maximum traction. Machined from a solid bar of Zirconium, the MONSTER Thumbdisk is 25% larger than the stock model without protruding past the scales. Drop in fit. This is THE answer to those hard to open knives!! *Does NOT fit the Hinderer FireTac or ZT-0620/30/40 series knives!*