The new Petzl Basic ascender is smaller, lighter, thinner, 8-11mm.
This video is a subjective comparison of the 'new' vs. the 'old' Basic.
Upon further evaluation:
Climbed with it rigged as a knee ascender on 11mm Blaze ... worked fine, IMO.
The 1/2" (13mm) line did work BUT NOT RECOMMENDED.
Overall ... the new Basic seems a little 'light-duty' for tree work.
In light of the ZigZag failure ... and the recent New Croll failure (also made of thinner stock); Petzl needs to stop catering to the crazies who weigh their shoe strings ... SAD.
I wish I would have bought more of the old style.