What are they:
The highest quality valve cores for presta valve stems which use removable cores. These can be used to upgrade or replace your existing valve cores in tubular, tubeless and high end clincher inner tubes.
So we've always noticed how really expensive tubulars had such nice valve cores with smooth edges and high quality seals that resisted sticking. When we started developing SILCA Tubeless valve stems, we set out to find the best cores, and realized that only a handful of companies make them globally. After a lot of phone calls, emails and discussions, we knew instantly when we had found the ones we were after. Fully CNC machined with roll-formed threads these cores give themselves away with their spun-formed tops that keep the valve nut from unthreading too far. Most companies crimp the threads here which damages them such that the nut cannot thread over..we find the extra effort to spin form a perfect little mushroom head on the top of the valve to really say it all: these are carefully made. Icing on the cake is the use of fully synthetic seals for both the stem seal and the core seal, this means that the core will resist aging and cracking for far longer while being significantly more resistant to both synthetic and natural based sealants if you are using tubeless. Best of all, this additional thought, care and attention to detail costs almost nothing over lesser cores while saving you pain and suffering over the coming years.