Yes, the tool holders are special collets that you install the end mill into and place it on the tool rack. The tapered design of the top of the tool holder allows it to be grabbed and secured by the tool changer.  Tool holders are available in 1/8", 3/16" and 1/4" shaft sizes.
Note: when you buy the Automatic Tool Changer, it comes with two 1/8" tool holders and a rack that will hold up to 5 tools, so to fill the entire rack, you will need to order 3 more tool holders.