The RT2-04-SD5-90 is the longer of the two Roof Tech mounting screws for its self-flashing PV mounting products, at 5.0 mm diameter by 90 mm long. Roof Tech lists it for the RT-APEX, RT-MINI II and RT-MINI I (rafter only) mounts; the 60 mm version is RT2-04-SD5-60.

The screws are stainless steel wood screws supplied with a conical washer. The RT-MINI II installation manual instructs installers to tighten until the conical washer stops rotating, to avoid impact drivers so the head is not over-torqued or broken, and to keep the screw at least 5/16" (7.9 mm) from the edge of the rafter.