If you want to tune your airsoft gun to the smallest degree then you need the Bioshot Tuner Pack. We have included all 4 of our competition grade sniper weight bbs in one pack. This is great when you don't want to purchase an entire bag of bbs until you know exactly which weight works best in your gun. Each Sniper Pack comes with 400 rounds in the following weights, .36g, .40g, .43g and .45g. Try all 4 weights through your airsoft gun to see which weight works best for you. Then you can go buy full sized bags without worrying if you are shooting the right weight or not.