The Comp Coil is a "Compression Spring" recoil reducing device.
Some Highlights of the Comp Coil are...

• The base and back plates are primarily the same as the Counter Coil's
• Aluminum and steel construction with some components that are yellow dichromate zinc plated
• The compression travel is approximately 5/16"
• The Comp Coil, without a mounted recoil pad, from outside of base plate to outside of back plate is 1" in length
• For large bore guns, no compression cylinder support is needed
• A hole 1" in diameter by 1-5/8" deep is needed for the compressing cylinder, so in most cases the Comp Coil can be mounted on semi-auto firearms
• The two guide pins need a drilled hole 1/2" diameter by 7/8" deep
• The Counter Coil installation fixture and drills will work for the Comp Coil
• Limited 5-year warranty