A British firm is now marketing a new type of prestressing cable anchorage, after exhaustive testing to determine what happens in end-blocks during and after prestressing. The result is a spiral anchorage intended for use with large diameter stranded cables. The design of the new anchorage is based on the assumption that the bearing area will be provided both by the end thrust plate and the surface of the spiral. An angle of 80 degrees with the longitudinal axis was found to be most efficient. The spiral acts as a continuous abutment which carries and distributes the load into the concrete over its entire length. This gradual distribution of force greatly reduces the danger of local stress concentrations. A further advantage is that the edges of all the spiral ribs are parallel to the axis of the anchorage, thus neutralizing any wedge action which would otherwise occur due to the body of the casting being slightly tapered. The upshot of this improved anchorage is that the prestressed concrete designer has a more compact unit which he can specify with greater accuracy and higher margins of safety; the contractor also has the advantage of compactness, reliability, and ease of installation without the necessity of using spacing blocks or local reinforcement.