I like chain guards. I have one on my 520. My other bike doesn't have one and it irks me. A chain guard keeps my socks clean. I'm all over form rather than fashion though. The Shimano ones are bulky looking. Weight to me, has never been an issue. I ride steel frames. I don't race. I need to find one for my other bike with an FSA crankset. I don't want to replace the whole crankset....yet.