Twice's quirk allows him to make clones of himself or other people (he can only make two) as long as he has their measurements. The clones possess the following properties:
The same powers, personality and memories of the original and also have free will,
They are not aware they are clones,
They are made in the image of how the original currently is.
They will disappear either when Twice dies or they take damage equivalent to a broken arm (although this varies).
As more doubles are made they lose more and more durability.