These clever supports let you compensate for shelf support holes that are not perfectly aligned. The spiral-shaped outline gives them a varying radius (pin height). Using a slot screwdriver, you simply rotate the spiral to adjust the height of the shelf within a 3mm (1/8") range to eliminate shelf rocking.
Made of ABS plastic. Sized to fit a standard 5mm (3/16") hole, they project 8mm (5/16").