Originally Posted by
schreff
The promo kit comes with the 6, 7, and 8mm restrictors. Not sure what other brand ones fit. I use the 7mm restrictor and haven't had a need to try anything else.
Mine only came with an 8mm but it was when they first came out. It also came with the #6 plug and I hear the new ones are coming with a #5.
Novarossi restrictors will fit the GRP