RS4 7.5g RS2 3.5g. Mine is the RS4 better battery life and range. Don't get the Marshall they aren't any good on a hawk, they are designed for longwings, and I would still get the Microsensory. My mate is selling his Marshall GPS after seeing mine in action and buying Microsensory. The battery life on the Marshall is shocking mate, and a recipe for disaster with a gos.
The other day my mate forgot to charge his Microsensory before he went out and the battery was a higher percentage when he packed up as the solar panels on the tag charged it as he was using it. Quite often mine is on 100%