I use this marker as my backup, it packs down really small and fits nicely in my drysuit pocket. The beast feature though is the no-lock inflator thingy - you can fill it either with your mouth, drysuit hose or bc hose. Unlike some other markers, you don't have to push the hose on and then push further to open the valve - press the hose on, it fills, pull the hose away, or just let it fall off as the bag heads to the surface. Greatly reduces the chance of the bag pulling your reg away, or even worse you to the surface. Super easy!