This spring provides an extra high degree of extension to the PIP joint. The coil springs are placed on either side of the joint. Pads are placed distal and proximal to the joint to distribute the pressure evenly. The front strap is adjustable with hook and loop. 
The force over the joint is approx. 12,4 N in full extension.

Length in mm. The distance is measured from the distal flexor crease in the volar region to the flexor crease on the DIP joint of the finger. The finger should be extended during the measurement.