Has 4 sizes. Strong neodymium magnets for attachment close to the worksite or toolbox. Cast from alloy steel for strength. Marked 1, 2, 3, and 4. 12050 #1 = KK #2 = K7 #3 = KG1 #4 = K30 12060 #5 = K4 #6 = K3 #7 = K32 #8 = K2 Each key has a number 1-4; #1 is similar to Jacobs key 'KK', #2 is similar to Jacobs key 'K7', #3 is similar to Jacobs key 'KG1', #4 is similar to Jacobs key 'K30' *#3 is very close to the size of the chuck key provided with the 17450 drill extension