This Precision Lighting L13550 recessed double contact plunger lampholder adheres to the strictest quality control and quality assurance procedures in the ballast and lamp industry. With an R17d socket and rated for 660 watts, this 600 volt lampholder is for use with T8 and T12 high output and very high output lamps. Each Precision Lighting product is tested under the toughest conditions and meticulously factory checked for defects in materials to reach you in perfect condition.