Eliminate the guessing, use this great tool from CRL and get perfect thickness on your insulated unit replacements. I found that the customers are impressed when you bring this professional tool out and explain how it works to your customer. They are assured they are getting the proper fit.

CRL CAT. NO. MG1500 Measures From Inside of the Building- No Glass Removal is Necessary Calculates Thicknesses of Insulating Glass, Laminated, Bullet Resistant, and Single Lite Float Glass Padded Carrying Case and Batteries Included Provides Fractional Measurements