Absolutely useless - ends up tightening the lens zoom also which does not allow the zoom to turn for focusing .Well made, inexpensive and works great!This tripod collar fits my Canon 70-300mm F4-5.6 L IS USM lens perfectly.It is heavier than the original Canon collar and the paint is the usual yellowish white familiar on most Canon L Zooms. My 70-300mm is painted the greyer tone also used by Canon so the two are different colours. It doesn't bother me but I mention it because it will bother someone.Functionally the same as an authentic Canon collar (there is some metal rub if you aren't careful when twisting, just like the original). Not quite as polished a product with some finish issues, but at a tenth of the price of the Canon Collar I can live with it.Collar opens smoothly and tightens securely. If you need a collar and don't wish to spend $220+ on the original, this will satisfy all but the pickiest of people.