Every bike needs a test light in the tool bag and they usually vibrate apart or poke through the bag. We love these insanely durable brass test lights from Germany. The screw-on cap covers the needle and the bulb is completely protected inside the body. Our buddy Walter at Kickstart Cycle Supply improves them by adding 36 inches of modern 16-gauge, insulated, cloth-covered wire, soldered connections and a stronger clip. Literally, this is the last test light you’ll ever need.