The RuiXing Throttle Shaft Butterfly Screw holds the butterfly to the throttle shaft in most Clone or Predator Carburetors. 

This is the stock screw used in the Ruixing carburetor but fits many others. The difference in brands is usually the head shape and size and the overall length. This is important for those who build their own carburetors to maximize the flow according to the rules.

The RuiXing Butterfly Screw fits most Clone Carburetors, including the Tillotson PK-1, Hyuai, Ruixing, and SP Carburetors on the Honda GX200, Ducar 196, Ducar/Tillotson 212E, Tillotson 196R/RS, Tillotson 212R, Ducar/Tillotson 212E, Predator 212, and BSP 196 and 212 Engines.

AKRA 2020 Rules for Throttle Butterfly Screw

Butterfly .037" thickness. Butterfly screw minimum length .305", the screw must remain stock as produced with no alteration allowed to achieve min length.

NKA 2020 Rules for Throttle Butterfly Screw

40.4.11.6: Butterfly 

The butterfly is .037" min thickness; butterfly screws minimum length 0.305".