Do you have the batteries? I use two 18350 on my Rick Trent laser. When it advertised to run two 16340 when using to shorty setup . Do you have the batteries? If they fit it will not only work but will give you more battery life. If you don't have them , and your 16340 have some wiggle room, the 18350 will most likely fit as they are a bit wider. I hope that help a bit.