I have been using Simon's SRM gear shifter set for a couple of months. TL;DR they are excellent and come with different arm options in carbon fibre and aluminium, the carbon fibre being a little quieter and a slightly 'softer' feeling change.. Should you buy them... Yes you should.
They arrived beautifully presented in a tin with custom cut inserts for all parts. All tools, bolts, nuts and leads are included as well as two sets of magnets... stronger and lighter so the shifters really are customisable in every conceivable way. On top of this all the parts are made to be user serviceable and replaced. This, to me, is a real sign that the product has been well considered and built genuinely with the end user in mind. A rare and refreshing thing to find people creating for the benefit of others and not just the bottom line.
I run a racing school where we chase every possible little advantage out there. The confidence of never missing a shift allows me to focus on the road ahead and is one less thing to worry about. I highly recommend this product.
Jon Edwards, Driver Coach at Total Sim Sport Race School .
If you've used magnetic shifters before you'll be right at home. My only other reference is Martin Ascher full carbon shifters (back when Martin owned the company). Simon's product matches the standard of the Ascher shifters and both are excellent to use. Simon's shifter are more customisable and therefore are my preferred option. They will be a staple of all future wheel builds.