The abrasives are great, but the brass adaptors/nuts are rubbish. The thread they used is either not standard or is just really poorly done; my dad is a Tool and Die maker, and he said he has taken it to work and not been able to find a single tap or bolt which fits the brass nut. When I asked the supplier what the thread was, they gave me an answer (6.3mm which is roughly equal to 1/4"), but absolutely no 1/4" taps currently made have the thread spacing found in these nuts. I highly recommend you change the thread to a common metric or imperial size. Use a tap which you can purchase from another manufacturer, because as it stands, these are useless to me. Would not buy again, even though the stones are good.