What barrel do I use for my Paintball gun?

Okay I was planning on getting a better gun to use I found one but I'm not sure what type of barrel to get for it. When I am asked the question of which type of barrel I want it says er or spyder and being barely experienced in the sport I don't know which one to get. I decided to go with the Azodin Blitz but I want a longer barrel, to add accuracy, but I'm not sure which type of barrel I'm supposed to get. If anyone can help it would be greatly appreciated.