Standard Speed Feed will fit any and all Halo/Reloader shells that are NOT the new magnetic lid ones. It also fits all the "clone" types I've seen based on original Halo shell. And it fits the Pulse just fine.
Simple maintenence will keep it that way. If Speed Feed fit loosens that means you've been keeping it on your hopper in your dank, dark and stinky gear bag. Pop it off and keep it out of the bag until next you play and the fit will be tight again. If the reverse is true; it's very tight and stiff put it in a sealed sandwich bag with a couple drops of water for 2 or 3 days and it will be perfect.
There is an adapter coming for the magnetic lid Halos but I don't have a date yet for release.