Exotek Racing - F1Ultra Titanium Rear Axle, Lightweight Ball Diff Axle Upgrade Parts RC Multirotor The Progressive Knife (PK-2) is

The Progressive Knife (PK-2) is a new model and the Thunder Spear has a built-in folding gimmick allowing for greater pose and play variety

- 180mm in length with a 0 to 10 deg adjustable angle

Open/close function

straps tied to the center of an axle are useful to limit the suspension from unloading

Exotek Racing - F1Ultra Titanium Rear Axle, Lightweight Ball Diff Axle Upgrade Parts RC Multirotor The Progressive Knife (PK-2) isLight weight 1 4" titanium axle replacement for the Exotek F1Ultra ball diff for more rpm's and lighter rear pod movement. About 10 grams lighter than the stock steel axle yet stronger than comparable carbon fiber or aluminum axles. Direct replacement for the F1Ultra.