I am sure this may be redundant for the longtime air rifle shooters but it was big news to me. I own a Diana model 36 .177 and Ruger Yukon .22. The Diana I inherited so I used the pellets that came with the gun and was not to impressed with the size of the group at 40 feet or so, but thought that was the nature of air rifles. I bought the Ruger from Pyramid Air and while waiting for it to arrive read the reviews. Almost every one said "buy the pellet your GUN likes....NOT you"...So I bought several and was amazed at the difference a pellet could make in the grouping. From a group the size of your palm to one the size of a nickel! Having shot .22 rimfire all my life and several other guns, a change in ammo was no big deal, with airguns it is everything. Just my 2 cents....good shooting.