What is the difference between ETS23 and ETS33 electronic trips?

What is the difference between ETS23 and ETS33 electronic trips?

The ETS23 trip unit is for the  UTS150 and UTS250 frame MCCBs. Alternatively, the ETS33  trip unit is for the UTS400 and UTS600 frames. Functionality and adjustments will be the same, as seen below.