(More customer reviews)It is a two-lamp socket. It worked perfectly for my application (created a home-made grow light for growing vegetables from seed).
No washers or nuts are included with this. Most hardware stores carry what you need, though.
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Twin cluster fixture socket. 1 8 IP Male threads on each end. Medium base, 6" wire loads. 18 gauge, 105 leads, 660W 250V. 4 1 2" high. UL listed.