These Searchlight branded halogen G9 bulbs are fully compatible with normal dimmer switches, and do not require a transformer. The small size of G9 halogen capsule bulbs means that many modern decorative light fittings utilise a G9 bulb, as they will fit in small glass shades where standard bulbs wouldn't fit. (When installing a halogen bulb, make sure that you do not touch the glass part of the bulb with your bare skin - e.g. fingers, as the natural oils from your skin can considerably reduce the life of the bulb).