GR10q 4 PIN 16W Light Bulb, 2D 4 Pin Bathroom Light Bulbs Warm White 3500K, Squ

4-Pin GR10Q Base: TobeBright 16W bathroom bulb features a 4-pin GR10q base, distinct from the 2-pin GR8! Easy to install, give the bulb a slight twist until it securely locks into place on the base.

eBay