I was curious so I Google it....
"Thermal Dissipator™
When it comes to transferring heat from your barrel, the JP Thermal Dissipator™ far exceeds traditional fluting and is intended for applications where sustained fire with excessive heat buildup is a problem, such as varmint rifles under hours of constant use.
Tests show that most heat resulting from sustained fire is developed in a 2- to 3-inch area in front of the chamber causing throat erosion and reduced accuracy over time, not to mention the problem of heat buildup in the hand guard itself that makes handling of the rifle difficult or impossible. Attaching this heat sink between the gas block and receiver will yield unparalleled heat dissipation by increasing the surface area under the hand guard by over 700% and providing more uniform barrel temperature under sustained fire.
The JP Thermal Dissipator™ is an anodized, deep-finned 6061 extruded 2-piece sleeve available in black, silver, red or blue, giving a dynamic appearance when installed under a JP high-grade hand guard.
A great upgrade for any JP rifle, upper assembly or barrel kit, this part fits any of our current production JP Supermatch barrels and can also be used on any barrel recontoured to .650" or .750" under the hand guard. Click below to see the dimensions of the individual models to determine if they will fit your barrel."
http://www.jprifles.com/1.4.5_hs.php