There can be some cooling issues, the sleeves could get out of round a bit if you don't bore it afterwards and on top of all, I don't think they do any good. I've seen sleeves crack with block guards and I've seen them crack without so they really don't solve any problems.
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Don't bother giving me "rep", I won't return it and I think it is stupid.
Gracie Barra Clearwater
Gyms in Clearwater, St. Pete and Port Richey
pm me if you are interested in trying a free class at any of the gyms.