I use two of the Evolv USB chargers and they charge my batteries to exactly 4.20V.
LiPo charge cycles follow a CC-CV algorithm. First, current is held constant (500mA in this case) while the voltage increases. When voltage hits 4.2V, current starts to drop, but the voltage stays at 4.20V. The light turns green at the end of the charge cycle, when current draw at 4.20V drops below some threshold, probably in the 10-50mA range.