Includes the right and left hand bearing holders and 2 stub axles. Requires a total of 4 ball bearings, 2 each side that must be ordered separately. The Double Bearing Holders are a direct replacement for the single bearing holders that come with the Plafit SLP1 chassis kit. And everything is a direct fit. The Double Bearing Holders can be adapted for use on the SLP2 chassis kit however it will require the use of Front Axle Blocks (ie. PF 1704A,B,C,D,) and screws, etc. that do not come with the SLP2 chassis kit.