Allstar 1 inch Tall 4 Hole Square Bore Aluminum Adjustable Carburetor Base Plate is an adjustable model for a 4150/4160 series style carburetor It has a 4 hole square bore design It is 1 inch tall and constructed from quality aluminum material It is also known as the "governor" It a is a four-hole aluminum spacer with tapered inserts which may be quickly changed after removing the carburetor The base plate restricts air/fuel entry and reduces power slightly to prevent wheel spin The inserts range in size from 0 950 inches to 1 400 inches for custom tailoring for quicker lap times and are sold separately in packages of 4 pieces It is backed by a 90-day limited factory