This fret contains 32 Mk3 delayed action autocouplings for use on 4mm scale layouts. They have also been successfully used in 0-16.5.
The recommended minimum radius curve for these couplings in 4mm scale is 2′. For tighter curves, use the MP4 mounting plates. They also have the added advantage of making the couplings easier to fit.
To fit and make the couplings fully operational, you will also require BW brass wire, NSW4 nickel silver wire, SIW4 soft iron wire, and permanent (4MAG) or electromagnets (PK MAG). Alternatively, you could just purchase the S/AC4/3 starter pack, which contains the fret, the wires and four permanent magnets. A cheaper trial pack (T/AC4/3) is also available, with eight couplings and mounting plates, wires and one permanent magnet.
The actual size of the fret is 92½ x 144mm; it is etched in 0.015″ brass. Each coupling is 32mm long and 10½mm wide.