I can't imagine putting armor all or black magic on the belts. I put it on my dirtbike seat one time and not only did it chap the hell out of my ass but it was slippery as hell. Not to mention I would think it could weaken the belt. We had to throw any chokers away that got oil on them at work.
Mine do the pull after the car has been off a few seconds but what I love about my seatbelt is it doesn't constrict like a boa constrictor. If I need to get in my pocket I can pull it out some or if it's getting a little tight I can get a little room. Some cars I've had to take the belt off it was f-ing tight and uncomfortable.
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