The BLP "R" series jets have the standard Holley® thread size of 1/4 x 32 that is commonly used in all gas carburetors and some alcohol carburetors. These jets are available in a standard length and an extended length for drag racing. The jets are available from .055 to .173 in .001 increments. Please note recommended torque value for the 5550BX series jets are 15 inch lbs. Max torque value 16 inch lbs. this is based of the largest jets size in this series (.173).