Received 2 for a couple my cans, returned them. They aren't very tight fitting, with the fire sleeve units are 5oz, just wasn't for me. Ordered a few more burn proof gear covers. They're are pricey, but they're the best in my opinion. I've tried can Chaps, Cole tac, tbac, t&k. The burn proof covers do a good job mitigating mirage. Yesterday was 35° and raining, zero wind. I could put 6 rounds through my 300 norma imp before mirage was bad enough it was affecting my aim at 400y. Same cover on my 6cm and 65prc, was able to shoot bout 8-10 rounds through those. Warmer days with a lil breeze, you can shoot more rounds before mirage becomes a problem, even tho should be letting barrel cool before that.
I know a lot of people make the argument of not needing a cover while hunting, but a friend and I were shooting in the field couple weeks ago, and it was a dead calm cold morning. He had mirage in his NX8 after one round down his 7prc with no cover, I sent 5 out the 6cm with covered Wolfhunter can, still no mirage. How often are you shooting in dead calm? Very rarely, but every once in a while it happens.