This is a simple upgrade, consisting of four items (both struts and two steps); it improves on the kit items by a major factor in that you don’t have to glue what is a basic triangle with an angle as the kit would have you do – see the comparison picture below, where the kit-supplied oleo strut is separate from the torsion strut. On the real aircraft, this provides dual purpose action in that it dampens impact with the ground without causing the aircraft to rebound, which could result in really bad things with moving rotor blades.
(This was changed on some versions by using an “A” frame strut, replacing the torsion bar completely. This is the version Revell used for their release from 1987. I can’t vouch for the effectiveness of this modification, but it’s obviously a bit more sturdy.)