Extruder barrel cooling duct for MK5-6

I've some people mention that longer prints with PLA require active cooling. This duct is intended to replace one of the small plastic sides between the front and back acrylic plates for your MK5-6 style extruder.

The smallest fan I could find at the local electronics store was a 40mm fan. However, the front and back acrylic plates are only 35mm apart. This duct gives a mount for a 40mm fan, letting it blow air into a 40mm diameter cone, which narrows to 35mm, which goes to a 35mm wide d