on how old you are.
(And hence, your eyesight...)
The Halcyon SPG is a fine product and works great. So is the OMS. But both are the same diameter, and hence the numbers are smaller than the large Dive Rite SPG. I'm (ahem...in my prime) and recently started wearing glasses. Not only is the Dive Rite SPG circumference larger, but the numbers are more distinct and easier to read.
This may not be of any interest to those who essentially know their gas consumption and don't use the SPG often, however, its annoying to look at the thing and not be able to distinguish the numbers should you want to.
I exposed the Halcyon SPG and the Dive Rite to a dive light (in the shop), then took them into the pump room (which was dark). The luminescent back of the Dive Rite and the larger numbers made it a snap to read in the dark. The Halcyon SPG with its much smaller numbers, huge logo (which cuts down on the luminesence), and smaller face to begin with, was much more indistinct and nearly impossible for me to read. (I was wearing a mask with prescription inserts.)
Obviously, just my experience with just my eyes..., your mileage will no doubt vary.
Still, between the two there was a significant difference to me. FWIW.
