A couple of days ago I replaced the ST needle valve assembly in a Fox 35 with a PA needle valve assembly that Randy Smith makes specifically for the Fox 35. The ST NVA was a big improvement over the stock Fox NVA and Randy's PA NVA is, in my opinion, a big improvement over the ST. There is a better fit between the threads on the needle and those inside the spray bar. In addition, the nylon keeper in the collet is much easier to use than the collet on the ST. If you want or need to replace the NVA on your Fox 35, I highly recommend Randy's PA unit.