Had to double down on the posts about the same eBay guy that is selling the Cool Mag.  This is too good:



Made from .030 stainless chrome alloy that is practically rust proof, and YES it cools your barrel.
This serrated pattern is designed for maximum heat dissipation used in Hi-tech heat exchangers.
AR-fins are a two part system a primary rap around the barrel and a secondary sheet for added cooling.
It fits in all 6.7 inch Quad Rail Carbine Length 2 Piece Drop-In Systems.
AR-fins weigh only a few ounces and installs in minutes and LOOKS GREAT.
We utilize a precision crush fit using your Quad rail for maximum contact with the barrel and thus alleviating any possibility of rattle or noise from the fins.

If you don’t like this idea… bros do you even science?  

Sometimes the speed holes in your current quad rail just don’t cut it when it comes to heat dissipation.  If you’re not disappating the maximum amount of heat GTFO, and get you some fins.

The bid is currently at $40… get in! haha


Hat tip: Mark