Tascione

My question concerns compatibility of collets with my lathe. My understanding is there are two issues: the threads of the drawbar of my lathe and the length of my drawbar. How can I determine if a particular collet is compatible with my lathe, before I buy it? Thanks.

Do you know the brand -manufacturer of your lathe, and the size ( 6mm-8mm, etc ) ?
You can really narrow your choices down if you have the information.

Randy