Hi there Bob... As Paul says welcome to the world of paintball... The guys I play with swear by upgrading stock barrels... Improved accuracy etc etc... However i have a follow on question (I'm pretty new myself) for those with far greater knowledge and experience... With a freak set you get different diameters which i understand are for different paint / weather conditions and alike... However how do you determine which insert to use...? Do you make a note of it whenever you use different paint or do you trial and error when you're chrono'ing your marker before play...? Interested in other's opinions on selecting the right insert please... Thanks