i don`t know too much about the exact bore numbers. but i know that my trombone is a medium to large bore. and i find that my tone is a lot better on this horn. also, about F attachments, it really is not too difficult to learn to play one. you can still use the "normal" positions and can start switching slowly. there aren`t that many notes that have new positions anyway. (mostly just ones out in 6th and 7th position and those lower than D flat). a large bore F attachment can really help your playing abilities, but does not make or break a player. of course everything varies from player to player, so you`ll have to decide whats best for you. have fun and good luck! ~Michelle
