Basically I'm looking for a new chain for my bike. I'm looking at all these 7-speed, 8-speed, 9 speed chains, then there's Shimano, SRAM and ConneX to name but a few. My bike isn't anything flash - rather a budget thing, but it does for me. It has twenty-one gears in total - seven at the rear, 3 at the front. Bascially I'm assuming I need a 7-speed chain, but can I choose any that says 7-speed, or do I have to look out for anything else? Also, any tips for installing the chain would be appreciated.