The OK was intended as a preparation class for the Olympic Finn and it has followed its technical evolution ever since. The rig is identical to a Finn comprising a single sail set on a rotating, un-stayed, bending mast.

OKs are built in plywood, G.R.P and composite construction and all forms enjoy equal racing success. Freedom of choice in hull materials is replicated in choice of rig. The choice of mast, sail and fitting must fit within the class rules but enables the sailor to have a combination suited to his/her requirements. Consequently, every OK develops to suit the owner’s style of sailing, while the shape of the hull is defined by a comprehensive set of strict one-design rules ensuring a long competitive life span. Old boats often only need a rig up-date and minor constructional modifications to make them competitive, provided they meet modern buoyancy requirements.

In the 60s and 70s, the OK class enjoyed an explosive success, with the total number of boats exceeding 10,000, and large racing fleets building up. In the 80s, the success of the popular one-design single-handed Laser affected the success of OK.

In 2005, There was a revival of the OK class with many older boats being restored and updated, new boats are being built and participation in club races is on the rise.

The OK class celebrated it’s 60th anniversary in 2017.