OEM pistons, but I radiused the ports (not at all easy to do on those tiny things) and I partially blocked the 0.7mm bleeds with 0.5mm safety wire. I should have photo'd how I did it, it's not the easiest operation to describe. I'll photo it next time I have the forks apart. I think that the Ohlins inserts would be a big step in the correct direction.... ...but from an economic standpoint I don't know if it would be the best course of action. Putting $1000 worth of Ohlins cartridges into $1100 worth of 45mm ATAS parts tubes might be money thrown away. The ATAS tubes aren't as stiff as I'd like, and I still don't know if they will hold up over time. I'm one of the guinea pigs on the ATAS setup, I'll let you know how they hold up over time. Hindsight being 20/20 I should have rotated my tubes another time and waited to see what the 2020 AT has for suspension.