4 ring ones are ok (Ultimate styling), but they do have a problem with the fixings which are quite brittle, there are always ones being sold on ebay cheap due to the fixing studs breaking off. The 3 ring (ProDesign) are far higher quality but have not been available new since around 2005. I've both types, some on an F some on a TF. If buying second hand (4 or 3 ring) just ensure the fixing studs are all there. If buying new, just make sure you do not overtighten the nuts on the studs.