Tubular pin tumbler lock
A tubular pin tumbler lock, also known as an Ace lock, circle pin tumbler lock, or radial lock, is a variety of pin tumbler lock in which six to eight pins are arranged in a circular pattern, and the corresponding key is tubular or cylindrical in shape.
Tubular pin tumbler locks are generally considered by the general public to be safer and more resistant to picking than standard locks. This is primarily because they are often seen on coin boxes for vending machines and coin operated machines, such as used in a laundromat. However, the primary reason the locks are used in these applications is their lack of the depth requirement that most other locks require.
Such locks can be picked by a special tubular lock pick with a minimum of effort in very little time; it is also possible to defeat them by drilling with a hole saw drill bit. Standard tubular lock drill bit sizes are 0.375 in (9.5 mm) diameter and 0.394 in (10.0 mm) diameter. To prevent drilling, many tubular locks have a middle pin made of hardened steel, or contain a ball bearing in the middle pin.