Designed for 3.5 X 25 mm vials (not included). 3 x 25 mm should not be a problem. The little capsules are not cheap, about $18.50 each, expected to glow for 15 years. I get mine from a mad scientist in the U.K. Requires small amount of epoxy and your skill to bond it in place. Testing a set screw lock when I get mine, will update.