Many work lamps, dive lamps, and other lamps originally designed around the relatively inefficient automotive 9005 (HB3) or 9006 (HB4) headlamp bulbs can be substantially upgraded by retrofitting the ultrahigh-performance 9011 (HIR1) and 9012 (HIR2) headlamp bulbs. The 9011 and 9012 "HIR" (Halogen Infrared Reflective) bulbs are much more efficient by design, so they produce much more light, but they have the same wattage ratings as 9005 and 9006 (respectively), so there's no additional current draw or heat production.
When making this bulb swap, use only a 9011 in place of a 9005, and only a 9012 in place of a 9006. One of the three plastic base tabs of an HIR bulb must be slightly trimmed with a small saw, a file, or a Dremel tool to fit in place of a non-HIR bulb. The diagram below shows how to do so.
Fit problems are quite rare, but occasionally you may encounter a lamp into which the HIR bulb will not quite fit, either because of a casting ridge on the inside of the round hole through which the bulb shank protrudes into the lamp, or because the bulb base tabs are slightly too thick to rotate into position in the lamp's bulb seat.
In the first case, the casting ridge can easily be removed by wrapping a strip of 100-grit sandpaper around your finger, abrasive side out, wetting it so as to catch and hold sanding dust, and going round and round the bulb shank hole with your abrasive-wrapped finger until the ridge has been smoothed away. Use a damp paper towel to wipe the inside of the shank hole to remove the sanding dust, and then the bulb will fit right in.
In the second case, usually bevelling the leading rear edge of each bulb base tab with a file, dremel tool or sandpaper will allow it to twist securely into the bulb seat. Some lamps have bulb seats that can be adjusted for bulb base tabs of various thickness, because the seat is held to the rear of the lamp with screws. Simply loosen the screws slightly until the thicker base tab is accommodated.
But in most cases, there will be no such fit problems once you trim the top tab according to the image above.
(Please click on the picture at the top of the page to enlarge and print the modification instruction)