The main component is the drill chuck, which has a 1/2-20UNF thread and a capacity of 1.5-13mm or 2-13mm, depending on the specific model.
The set includes a chuck key, which is used to tighten and loosen the jaws of the chuck to secure the drill bit.
It also contains an SDS-Plus shank adapter, which allows the chuck to be used with a hammer drill.