The Kinetic Research Group LOP Spacer Kit is the length-of-pull spacers for the X-ray and Bravo Chassis. They can be used with the Whiskey-3 but will require the shooter to possibly source different screws. Each spacer is 3/8". The starting LOP for the X-ray Chassis is 12.8" approx for the Rem 700 version and 12.9" approx for the T3 version. Each pack comes with the screws needed for that specific amount of spacers, i.e. a 4-pack of spacers comes with two screws which are the correct length for using 4 LOP spacers. The 1-3 Spacer kit comes with everything you need for using 1-3 spacers, (3 spacers and screws for using 1, 2, or 3 spacers). The 1-3 Spacer kit comes standard with each X-ray and Bravo chassis. Fits: X-ray & Bravo chassis, will fit Whiskey-3 with different screws