The AU-DLM643 is a PAR20 lamp sized IP65 fitting with a cutout diameter of 90mm. It is fire rated and can be covered by insulation material too. It is suitable for use in Bathrooms. It takes a PAR20 lamp which can be CFL or LED. We recommend the AU-GUF4011 range of bulbs but others will fit also. Will not fit a standard GU10 lamp.