This must-have accessory is a stainless steel spring that goes around the outside of a standard lens housing and keeps the lens under tension against the diode module for more precise focusing. Easy to adjust and holds the lens position better than Teflon tape, which needs to be replaced periodically. This spring is sized for standard glass lenses so that there is still a bit of room to compress when the lens is focused to infinity. The ends of the spring are ground for smoother turning. Note: The spring may be trimmed with wire cutters in those circumstances (such as with a G-1, G-2 or red lens) when there may be insufficient room between the focusing ring and the diode module.