The Heliopan quality is a + for sure!
I'll second that. When I first started serious photography, I was living in Germany. It was so easy to get Heliopans there and they were quite reasonably priced, and the local camera shop recommended them to me. I've still got those 20 some years later.
Besides their filters, their step-up/step-down rings and their reversing rings for macro photography are excellent, too--made of brass rather than aluminium, work brilliantly. They're the ones I use for those purposes.