Check the listing for details. Command BT40 End Mill Tool Holder 3/16 3/8 1/2 3/4 inch B4E4 also works w/ Cat40. Condition: Used. Listed at 66.60 USD. These are being sold as singles, if you buy more than one, the rest will have FREE shipping. They are all in perfect working condition. They have the 16mm thread Pull Studs /Screws. These are compatible as Cat40 tool holders and Cat 40 machines, you just need to change-up your Pull-Stud configuration, or I think they can be manually installed in a machine easier.(I've even heard they just need to be turned 180 degrees when installing them?) Here is what is all here to choose from: 1A , 2A , and 3A are all for 3/16" or .1875" diameter milling bits. these are all Command B4E4-0187 1B is 3/8" or .375" dia. and is Command B4E4-0375 2B is 1/2" or .500" dia. and is Command B4E4-0500 1C is 3/4" or .750" dia. and is Command B4P5-0001 2C and 3C are 3/4" or .750" dia. and are Command B4E6-0750Please let me know right away what toll holder(s) you are choosing, I have to ship within 24 hoursIt is to your benefit to buy more than one, because of the free shipping after your first one deal.