I had to replace two units in my 25 year old speakers. As they were of a paper based material I was unsure about quality of reproduction in comparison with the polypropylene/rubber supplied. I need not have worried. The units were with me three days after placing the order and took 15minutes to fit. Apart from the fact that the electrical terminal connection were not the same as the originals I encountered no serious problem. I made temporary connections until I bought and fitted 4 of the right size. Sound reproduction great!