
DNA collet (left) works with your standard ER tool holders.
ER collets 6mm and smaller allow 40% of the collet to extend out of the collet pocket. This means 40% of the jaws surface area does not properly collapse on the tool shank because they are unsupported by the walls of the pocket.

DNA collets put more metal on the tool shank!
Small size ER collets have a large counter-bore in the I.D. at the bottom, (see illustration) that greatly reduces the amount of metal holding the shank of the tool. DNA collets have twice as much metal gripping the tool shank “in the pocket” where maximum holding power is generated as the collet nut is tightened.

Powerful jaws hold tools tighter - improve rigidity and T.I.R.
On ER collets 6mm diameter and smaller, the small jaws do not provide the holding force and rigidity on the shank necessary to produce acceptable T.I.R.