depends on quality really , some are very thin and a bit tinny, also if they are a uk outlet or overseas.
Mine are very good quality thick, stainless steel 90mm diameter tips which leaves a small gap for movement within the valance appertures .
They will allways clean up nice , cant recal what I paid for mine a few years back now but it was more than that to be honest, maybe have a look as sometimes there are good deals to be had but you need to go stainless really , 50mm is the outside dia yes , length is also a factor or they will stick out to far and you wont have enough space to get them fitted.