Winstone Wallboards Ltd are New Zealand's largest manufacturer and marketer of gypsum plasterboard, drywall systems, associated products and services. The company has been operating since 1927 and manufactures plasterboard systems under the GIB brand name. Winstone Wallboards Ltd, who have facilities in Auckland, Wellington and Christchurch, are part of the Building Products Division of Fletcher Building - a New Zealand based international company.

The GIB brand is a New Zealand icon brand and Winstone Wallboards have a proud heritage of being a New Zealand focused and New Zealand based company. Production of plasterboard started in New Zealand in 1927 and with it began the change from construction with scrim to plasterboard lined walls. Ever since regular innovations in the wall and ceiling market have kept Winstone Wallboards at the forefront of New Zealand building supply companies.