Traxxas Shocks GTR xx-long hard-anodized PTFE-coated bodies with TiN shafts (assembled) (2) (without springs)

To me, these are the single best upgrade on any Traxxas model I have had. Having experienced them on the Slash Ultimate, where they come as standard, I fitted a set straight away to my Rustler 4x4. The Ultras are ok tbh, but these just add a level of refinement to the ride quality and performance that is a true step up. They are super smooth and stiction free, with a large volume to absorb hits, so you don't need to go with thicker oils or stiff springs that cause compromises elsewhere. They are quite an easy build and fit. Just ensure you hold the shock upright with the air bleed hole at the highest point as you screw the cap on, else you will trap air. Fantastic upgrade.