PTC Etherification of a Phenol PTC Organics, Inc. Evotech Rear Spindle Bobbins Aprilia RSV4 (2021 2024). Features of Evotech Rear Spindle Bobbins for the Aprilia RSV4 Spindle Bobbin fixed on the driveline side Protects the costly swing arm and sprocket carriers Bobbin created from hard wearing nylon with an aluminium base Held through the rear wheel by a stainless steel spindle rod Red anodised hub stop on exhaust side Replacement bobbin heads are available to purchase What is Spindle Bobbin Crash Protection? Designed to protect the driveline side of the RSV4, the spindle head protrudes from the rear wheel hoping to receive impact before the swing arm. The inventive design allows the nylon bobbin to spin above the aluminium core which brings greater durability and reduces stress on the wheel. The bobbin is retained through the wheel using a spindle rod with an attractive red hub stop on the exhaust side.