The deeper you go, the more often you (should) check it – your Submersible Pressure Gauge or SPG! As divers, you make decisions based on cylinder pressures indicated by these very simple mechanical devices. With a quick glance, you want to be able to check your remaining air or other gas mix.
There are specific size differences between the various SPGs. Take the Halcyon Stage SPG, for example, which is small and lightweight, and compare it to the Halcyon Master SPG, with a large and clear display. You can also choose between a white and a black face.
Another type of gauge is the Scubapro Digital 330 Wrist Gauge. It is the ideal digital depth metre and bottom timer with a digital accuracy up to a depth of 330 metres, which makes this device highly popular amongst technical divers.