Review (5/5): RQ 12 is the only way to go.
This is the head (RQ 12) that originally came with my airtec razor. When they became dull I purchased the RQ 10 replacement. The RQ 10 was awful. It had a tendency to pull the hair out enstead of cutting it. I was about to look for another razer because of the experience. Fortunately I found the RQ 12 and there is a world of difference. If I'm unable to find another RQ 12 replacement, or maybe cutters I'll be forced to look for another shaver.