It can charge up to 77.8mm. It´s a 4-Slot(!)-version of the UMS2. UM2/UM4 have the same size but lower charge currents
The weakest point is the Slot-sharing, for me it´s more a 2-Slot-charger. For most cells I would prefer the Vapcell S4+. No slot-sharing, much better display, much more features (the UMS4 can only charge), more reliable for NiMH.