Do you want to verify what you're getting? We have advanced window tint meters to show you exactly what you're paying for, and we won't get upset if you ask! We enjoy doing this with our customers!!
Example This meter will read IRR numbers in three different ways. Full spectrum (780-2500nm), 940nm, and 1400nm.
Given the IRR can be measured in multiple ways, having the ability to measure at multiple points in the spectrum, along with full spectrum, can be insightful.