Upgrade Motoring Insulators – For Mikuni 40 PHH and 44 PHH Performance Carburetors with Mikuni Intake Manifolds. Black 1 Set – Part Number #Z70/050-R-BLK.V4. Version 4 with improved sealing capabilities.  1 Set includes two individual insulators and four o-rings. 1 Set required per carburetor. Insulators are ~1/4 inch thick. Center bore diameter is 44mm. Center stud hole to center stud hole spacing is 72mm. Precise CNC Machined – Made in the USA. Material is a thermoplastic polymer that is resistant to lubricants, solvents, gasoline and gasohol. O-Rings Temperature Range -20 to 400F (-29 to 204C). This Item is a Superior Quality Replacement for the Discontinued Mikuni Insulator Part #Z70/050. Uses Mikuni O-ring #Z70/075 or replacement alternative Z70/075-R. One pair of insulators required per carburetor. Also Fits Some Mikuni / Solex PHH OEM Carburetor Applications. For Solex OEM applications, Please compare images and measurements to your application for confirmation, prior to ordering. Also available in White #Z70/050-R-WHI.V4.