The 2+1 configuration allows for flexible configurations of the unit. The last axle on the booster can also be used to pin onto the main trailer to extend its axle group, if needed. The booster mechanism is equipped with a hydraulic relief valve and crush sleeves to eliminate an overload situation. There are 2 shim points on the booster to allow for fine adjustment of the axle grouping height. Multiple cylinder positions are available to allow for a wide range of operating weights on the unit.