The update is centered around the battery, moving from the 18650 up to the increasingly popular 21700 sized battery. The LED is also updated, out with the CREE XM-L2 and in with the more modern Luminus SST-40. The bigger battery and more efficient LED choice brings an output increase up to 1800 lumens, more throw (294m), much more runtime (1500 hours on “ultra-low”) and also a wider variety of battery choices:
Nitecore says to use High Discharge cells only and if it’s like all other Nitecore flashlights, flat top batteries are incompatible.
The Nitecore MH12S also upgrades the charging system to USB-C and a big bump up in ingress protection, from the IPX8 of the MH12 to IP68 on the MH12S. It is also compatible with the Nitecore tactical accessories ecosystem, including the NTR10 clip on ring, rifle mounts and remote switches. See image below for specific compatible parts. The Nitecore NTH10 tactical holster is included with the light.