Itty bitty Edison style 1/4 Watt lamp with a 3/16"/5mm screw base. (type E5 or E5.5) 1/2" long overall it needs 160ma @ 2.5 V. It has a clear glass envelope that collimates the light at the end for greater intensity when viewed end on. Typically priced around a buck a each. Great for science fair projects. model railroading or anywhere tiny light is required.

This 12V 35W Racing Series halogen lamp is made for automobile use and comes with a matching gasket and a 1/2" deep lens with a slight amber tint. (You'll need to epoxy the lens on if you're not mounting the lamp in another bracket.) Bulb is 2-1/2" wide x 1-11/16" tall x 1-1/2" deep with a 2-pin connector. Pins are 1/4" apart on the outside.

No, not knives. These are bayonet bulbs, so named because you push them in and twist, just like mounting a bayonet. Our each is a 2-pack of 12V 8W bulbs, most likely for automotive use.

From NAPA, packages of (2) high-temperature headlight sockets. You pick: #787110, 9006 2-wire, 1-1/8" wide x 5/8" x 1-1/4" deep with (2) 5" leads or  #787138, 9005 2-wire, 1-1/16" wide x 5/8" x 1-5/16" deep with (2) 6" leads.

Our each is (2) 50W,12V halogen bulbs with standard GU5.3 bi-pin bases. For low-voltage systems, bulbs are 1-7/8 dia, MR16 reflector flood lights with a 30-degree beam spread.