Being a noobie to clipless, I love the M520s. Easy to clip in and out but still solid with the retention just one click shy of as loose as possible. I installed them myself with no pedal wrench. I think it's 14mm, but any standard wrench will do, you don't even need to get them that tight, they will tighten as you pedal. Just be careful not to cross thread them, grease the threads and remember that the left pedal threads backwards.