Contact Mike at OPTICS HQ for that info. I do know there is no single mode head. The default is high then low. And the lens is 1/8th in thick glass. Doesnt look like the coated stuff.
I guess I'm a little disappointed that there is no single-mode head yet, especially since this product is advertised to attach to various SF Classic series lights. If I wanted multi-modes, it would seem to me that using the OpticsHQ multifunction tailcap would be the way to go.
Can you test more completely how the user interface functions (although my assumption is that these TH upgrades have the same UI as the 2-stage E-series upgrade heads -- a tailcap press within a second or so of the previous one switches modes, a longer delay resets the mode the the default)?
Initial press -- High mode (which is the default). Count one-thousand-one. Press the tailcap again. What mode do you get?
Reset the light (e.g., unscrew the tailcap and re-screw it). Initial press -- High mode. Count one-thousand-one, one-thousand-two. Press the tailcap. What mode do you get?
Continue in this fashion, incrementing the count, presumably until the light doesn't enter Low mode. That gives you the time delay needed to get back to the default mode when pressing the tailcap, or conversely the time window for which the next tailcap press switches modes.
The other thing I've seen in some multi-mode engines is that the time window varies with the voltage input. Drive the drop-in with a single 3.7V cell and you get one time window (I got about 10 sec for one 6P drop-in product). Deliver power from two cells and you get a shorter time window (for the same product, I got about 2 sec).
If you can drive the OpticsHQ TH with say two 123A primaries (presumably delivering between 5-6V, then two 3.7V Li-ions, and then three 3.7V Li-ions, that would probably cover the likely range of voltages where there would be any variation in the time window.