Measuring from the handguard cap, the base which clamps around the barrel is about 1 13/16 inches (about 46mm). The sight itself curves up and forward from the base and takes up about 2 1/4 inches overall (about 57mm).
The manufacture does not provide the dimensions of the base. It appears to be very close in size to the A2. You will have to reach out to Precision Reflex to confirm here: https://www.precisionreflex.com/ContactForm.aspx?PAGE=Contact%20Us