Installed on a Craftsman as a replacement for the original, which had badly mangled blade-engagement pins. The OEM (Original Equipment Manufacturer) was smaller overall, and had an oval shape. This unit is much brawnier and heavier. That is not a bad thing, as rotating mass acts as a "flywheel" and helps keep the blade from bogging down when it hits tall grass. The Stens fit on the crankshaft with minimal play; I recommend putting a little anti-seize on the shaft so the adapter can be removed in the future. No vibration, so it is a balanced part. Very happy initially, and if it is durable it's an excellent value.