When it comes to multifaceted reflector bulbs, it doesn't get any bigger than the MR18. At 9/4 inches in diameter, MR18 light bulbs have a larger beam spread than any other MR lamp and are ideal for applications where a large amount of directional light is needed. Here at BulbAmerica, we carry an extensive selection of brand-name MR18 light bulbs designed for a number of specific applications, including projector lamp replacement and medical and scientific equipment replacement.