LiftMaster 15-48B10GXX Sprocket For Commercial Openers that are 1/3 & 1/2 HP. The replacement sprocket is part of the Output Shaft Kit. The 15-48B10GXX sits in front of the Flange Bearing on the output shaft and is located outside of the frame of the opener.
This replacement sprocket has a diameter of 3/4". If the part number doesn't match yours don't worry! This item is also known as 1548B10GXX, 15-48B10G1, 1548B10G1, and 155009.