From OS Doors website:

O&S Doors Ltd celebrate 25 years in business which will be commemorated at our 410,000 sq ft state of the art manufacturing facility in Benburb, Co. Tyrone, Northern Ireland.

Our factory in Benburb employs over 360 highly skilled workers that specialise in 5Piece, Edged, Painted and Vinyl door production. We produce around 60,000 individual doors each week. We offer a superb online ordering system containing over 6,000 door styles and finishes available