Flowlights give flowtoys a good weight but if you like a heavy feel to your tools, you can add flowmass to the ends of your flowtoys -where they count- to give them more momentum. The mass can be installed onto crystal cases, all flowpoi, staffs and other tubing based flowtoys. If installing onto tubes, apply a tiny bit of vaseline/ petroleum jelly/ chapstick to the insides of the mass BEFORE installing on tube. If installing onto crystal case, do NOT apply any lubricant otherwise the mass may fly off while spinning. Flowmass is sold by the piece. You need two for a pair of POI or a STAFF. Please note that flowmass do not fit on flowlights alone!