GVM672S is the upgrade version of GVM520S, there is 672pcs LED bulb compared GVM520S only 520pcs, and it is brighter. Same function as following: Multi-function control: Master/ Slave and 12 channels function: you can set 12 different channels, and each channel can control more than 10 pcs GVM same series of video light. Only need to choose one video light in master mode, and others in Slave mode. That means you can control about 120 pcs video light.