Lisle 57440 Socket, 15mm This tool is used to remove and install belts on serpentine belt systems using the spring loaded idler pulley Fits idler pulleys requiring 13mm, 14mm, 15mm, 16mm, 18mm, 19mm hex and both 3/8" and 1/2" square drive sizes For more information check the main Lisle tool- 59800 Replacement part for Lisle tool- 59800