i use the etek 4 as well and i got one most of the parts will work with it but the main reason i got this package is for the 004 NBR 70 o rings thats not in the included parts kit. i lost one of my o rings on the oops asa so now i dont need to worry. if you dont have the spare parts kit that came with the gun buy this if not then i see no real reason to get it. works great if you friends use planet eclipse markers