ER Collets?

[DennisCNC]

What is the difference between them? Like ER20, ER25, ER30 ....
Will one chuck be able to take a few different ones or I need a chuck for each number?

[haysys]

Hi,

Each ER series represents a unique configuration of collet, and each requires its own size chuck. The larger the number the larger the overall size. The ER40 is big enough that you can get collets that will accept a 1"+ shank.

[CNCgr]

http://www.aseervadh.com/er_collets.html