They hold really well. I have thick hair (5" pony) and a 3" barrette will hold a half-up for me, and that's asking a lot. A French-back barrette will hold more hair, but for my hair at least they're too damaging so I won't wear them.
Former longhair, now CG, living in N. California where the fog meets the wind
3a/b, fine, normal porosity/elasticity, high density
Conditioner wash and style, sometimes with a dab of BRHG.