For spacing vertical reinforcement in columns etc. The wheels clip onto the reinforcement bar and minimise the area of spacer at the form face.

Concrete Cover (mm)	Bar Dia	Quantity
15	4 - 12mm	1000
20 / 25 / 30 / 40 / 50	8 - 12mm	500
25 / 30 / 40 / 50 / 60 / 75	12 - 20mm	250