found at Wiggle
Technology The S-Track cleat offers a 200mm² of cleat-pedal contact surface in all circumstances using the 2 mm wedge but an additional shoe sole-pedal contact surface area of 460mm² can be achieved by a simple adjustment. The main advantage of this operation is the significant increase in the contact surface area (460mm²)for unequalled power transfer, which makes the S-Track a formidable XC weapon. Adjustment of S-Track cleats procedure: For the most demanding mountain bikers, a simple adjustment is possible by sliding the wedges of different thicknesses (0.5 mm - red - / 1 and 2 mm - black) under the cleat, without the need to remove it completely. This ensures that cleat height is adjusted to obtain perfect contact between the your shoes sole(regardless of the type of shoe) and the pedal.