I just finishing converting my 2 C cell Mag to 3 - 123s. I was trying to decide what to use for a spring. I pulled the tailcap off my 3 C cell Streamlight Twin Task and saw that the spring is wound tighter than the Mag spring at the end so it would make contact with a 123 battery. I tried it in my Mag tailcap and sure enough it fit perfectly. Now I need to call Streamlight tomorrow and see what it costs to buy replacement springs for the Twin Task so I can keep one in the Mag. John