They are REI Taku pants. They have an elastic drawstring at the cuff, but I don't want to cinch it super tight. I usually have the elastic pulled to the "straight leg" configuration, with the gusset zipper closed.

@badmother, good idea about filing the teeth. I would, but I would only run the solid ring in the winter. When I am unladen with all the extra cr@p in the summer and have no pant leg to get caught, I would put the big ring back on.