Attaching accessories to the multitasking tool can be done in two ways. If you buy an accessory with a smaller shank, you'll also need the correct collet size. Collets are available in a set that can include all sizes or individual collets, and it’s important to check for these specifications to ensure you won’t have to file a return.
On the other hand, you don't need collets if you have a multi chuck. Because a multi chuck accommodates Dremel attachments and shank sizes, it functions similarly to a standard drill chuck—and to add to its functionality, you don't need to tighten it any farther than hand tight.