British Rail Brake Standard Open (Micro-Buffet)
BR Mk 1 BSOT, no. 9015 at Swanage on 13 April 2006. This coach is preserved on the Swanage Railway and is painted in Southern Region malachite green. It was converted from BSO 9229.
In service	1952–
Manufacturer	Mark 1: BR Doncaster & Wolverton, Mark 2: BR Derby
Number built	Mark 1: 18, Mark 2: 8
Fleet numbers	Mark 1: 9000-9017, Mark 2: 9100-9107
Capacity	Mark 1: 31 seats, Mark 2: 23 seats
Operators	British Rail
Specifications
Car length	64 ft 6 in (19.66 m)
Width	9 ft 3 in (2.82 m)
Height	12 ft 9+1⁄2 in (3.90 m)
Maximum speed	90 or 100 mph (145 or 161 km/h)
Weight	34 long tons (35 t; 38 short tons)
HVAC	Steam, electric, or dual heating, ETH index (Mk1 3, Mk2 4)
Bogies	Mark 1: BR1 or Commonwealth, Mark 2: B4
Braking system(s)	Vacuum, air, or both
Coupling system	Drop-head knuckle coupler on draw-hook (dual)
Track gauge	4 ft 8+1⁄2 in (1,435 mm) standard gauge

A Brake Standard Open (Micro-Buffet), often abbreviated to BSOT or BSO(T), is a type of railway carriage used by British Rail.

These coaches were converted from a Brake Standard Open (BSO), by replacing one passenger seating bay with a counter for serving food, and space for a trolley for light refreshments. The toilet was removed and the space converted to a steward's prep-room and store.

Two batches of coaches were converted, as shown below.

These coaches are no longer in scheduled main-line services, the last being withdrawn in the mid-1990s. However, several coaches from both Mk1 and Mk2 types have been preserved on heritage railways, or are used by charter companies. These are detailed below: