The versatile TEC Isotope Triode Fob is designed to hold several glass tritium vials (not included), which will glow continuously for many years without the need to charge it from sunlight or UV light. This version of Isotope Fob has 3 individual bores to house the tritium, hence the nickname "Triode". The Triode can hold several combinations of tritium vials, as each bore can hold either one 3mm x 23mm vial OR two 3mm x 11mm vials. Think of the color combinations! The TEC Isotope Triode Fob has three primary bores to hold the tritium vials, and the six grooves on the side of the housing provide maximum tritium visibility, yet offers superior protection of the glass vials. Once the tritium is installed, you simply insert the included rubber plug (spares included), install the o-ring over the post, and attach the split ring. This prevents the tritium vials from sliding out, yet provides an easy way to remove the vials if you want to change or re-position the colors. Complete your EDC collection with the functional and stylish TEC Isotope Triode Fob, which provides just the right amount of light for locating items in the dark. Perfect for attaching it to your keychain, camping gear, zipper pulls on gear bags or jackets, or try it on the pull chain on your ceiling fan. Where will you clip yours? Isotope Triode Fob Features: Custom designed with 3 bores Each bore can hold one 3mm x 23mm vial OR two 3mm x 11mm vials Combine different colored tritium vials for a beautiful effect Grade 5 titanium housing Bead blasted, uniform matte finish What you get: (1) TEC Isotope Triode Fob Packaged with (5) rubber plugs for tritium vial containment (3 required plus 2 spares) (2) O-rings (1 required plus 1 spare) (1) 11.1 mm [7/16"] diameter split ring for attachment to other items Important Note: Product DOES NOT include tritium vials