This protective case is designed to hold both the Dunlop CG/4 Camber Gauge (Part No. 3122, sold separately) and the Dunlop CG/5 Caster Gauge (Part No. 3123) at the same time. Metal case includes protective hold-downs designed just for Dunlop gauges.
If you have just one of the two tools, a little modification could make the extra space useful for holding other related tools.