Doesn't really matter. Get whayever you can find at a good price and good condition. I've put them together with both heads and I like the GSR more but I wouldn't justify buying the gsr over a b16a if you can find one at a better price.
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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.