The most popular chuck keys on JacobsChuck.com in 2016 are KG1, KK, K0, K0M, K1, KGA and K1M, which range in size from 1/8 inch to 9/32 inch. All the most popular sellers have 11 teeth except for KK, which has ten.
The most common Jacobs Chuck Key model is KG1. Its pilot size is 1/4 inch. The next most common is the 9/32 inch model KK followed by the 1/4 inch KGA. Models K0 and K0M are 1/8 inch and models K1 and K1M are 5/32 inch. The next most common models are K2, K3, K4 and K5, which range from 1/4 inch to 7/16 inch.