Grose Jet float valve for all side-float SU carbs. Ref: SIE0045.
Ansel Grose re-designed the carburetor needle and seat valve. His idea was to use a ball bearing that would constantly present a new surface to the seat and therefore provide a consistent metering of fuel. A large ball was used as the surface that the float would act against while a smaller ball would come in contact with the seat. This prevented the wear patterns that developed into the commonly-used brass or even viton SU needle and seat on SU carbs.