Low voltage spot bulbs have a 2 pin push in connector. The pins are often quite sharp and do not have 'feet' at the end of each pin.
There are various types of low voltage spot bulbs. They are often called MR16, MR11 or MR8. These names refer to the diameter of the front of the lamp, in 8ths of an inch. MR means 'multifaceted reflector'.
Sometimes the different bulbs are referred to by the distance between the center of the electrical pins. GU5.3, or GU4 are the common sizes, which are 5.3mm and 4mm apart.
MR11 bulbs have a diameter of 35mm, or 11 x 8ths of an inch. They are popular in small spot light fittings, track lighting, and some modern cooker hoods. They are available in a variety of voltages and wattages.
The 12w version of these lamps are the most common. The open-fronted version is often used in fibre optic Christmas decorations.
Sometimes MR11 bulbs are referred to as GU4 spot bulbs because the center of the two pins are 4mm apart.
AR111 bulbs are 111mm in diameter and 55mm in depth. These halogen capsule bulbs have a G53 lamp cap.
AR111 have an aluminium reflector which means they are heat forward, this helps to keep the light fitting cool. This makes the lamp ideal for use in spot lights and for display lighting. They are frequently used in restaurants, bars, nightclubs and retail shops.