It’s kind of a mess, but the new model that’s been in use all year is the Rookie EV. Unfortunately no one really knows that because none of the Karts have the model designation on the floor pan as the other OTK models do.
The Rookie chassis from 2016 and before is an entirely different chassis. The Neos from 2017/2018 was meant to be the big step forward to finally take it to their competitors and it had a pretty lackluster reception. The Rookie EV was basically the “back to the drawing board” moment, and they really nailed it. So, despite the name, it doesn’t have much of anything in common with any of its predecessors aside from wheelbase. (Different geometry, material, ride height front/rear, seat, axle, spindles, brakes.)
Edit: Just an addition, but the kart has been ridiculously easy to work with. Majority of the tuning being done is simple rear width adjustments, caster, and tire pressure. Front ride height always low, and we’ve run the A axle in everything from high grip with 100 degree temps to cold and rain.