Never buy bikes, parts or accessories online. Going into your local shop, asking a myriad of insane questions, tying up the staff’s time, then going online to buy is akin to sleeping with your best friend’s wife, then having a beer with him after. Online is evil and will be the death of the bike shop. If you do purchase parts online, be prepared to mount and maintain them yourself. If you enter a shop with parts you have bought online and expect them to fit them, be prepared to be told to see your online seller for fitting and warranty help, or pay a 20% surcharge.