We now have filters to ALL of the lights now, even the SR90
The SR90 and 91 both use the same power source. You can purchase extra battery packs and there is also a car charger for them as well. The batteries do not have to be connected to the head to charge, so you can have a spare charged up and ready at any time.
The SR91 has the longest run time and is nearly as bright as the SR90. If you don't turn them on at the same time you could not tell the difference. The SR91 is also lighter. Stop by at the next show to demo both lights. See you there!