The new version retracts do not only contain an improved retract mechanism but also a next generation control unit.
SLR Retracts: including tires with aluminium hubs, struts and electric retract system.
Best in class retracts for e.g. the Hawker Sea Fury
ESM Retracts: including tires with aluminium hubs, struts and generation 4 electric retract system.
Best in class retracts for e.g. the MIG