Screw capped spot bulbs also run at mains voltage. They are available in a range of sizes with variety of different screw caps. They are used in surface mounted fittings, recessed downlights and outdoor lighting.
The name of the bulb is determined by the diameter of the reflector part of the bulb. 'R' bulbs are descibed in mm, e.g an R80 bulb has a diamater of 80mm. The less common Par bulbs are described in 8ths of an inch, e.g. a Par38 bulb is 38 x 8ths of an inch.