@Gunsby_Blazen, it's about .725 (±.025"). Measuring things freehand doesn't yield the most accurate results.
It's a very low profile, 2 piece design. The dovetail adapter is a steel piece that fits into the Ruger SR9 sight dovetail. Machined into the adapter is another smaller dovetail to adapt the JPoint optics. I recall Eric mentioning that the dovetail is the same spec as a Glock's factory cut so you can also install other optics/sights if you wish(?).
I might be able to shoot it tomorrow as I got it installed tonight. Wasn't too bad to do, just had to take care not to damage my factory sights. Will need to get it close and dial it on in when I go. In the pics I took, I left the battery out, I'm unaware how fresh it is, but don't have any readily available to replace it if it dies on me. It does work and light up the glass as it should.
The JPoint snaps on and bolts into the aluminum plate that fits the steel adapter plate. There's a cover for the entire optics piece that's handy if you keep it in a range bag most the time. There's no ON/OFF switch so I believe you must remove the optics to take out the battery, unless battery drain is so minute that you could afford to leave it on 24/7 and check it regularly. I don't know about that, but it's a concern. A bit bulky for duty around the house, but for a range/competition gun, it should be perfectly adequate.
Link to Photobucket album.
Josh