YES 20 Sash Storefront System for Monolithic Glass STOREFRONT SYSTEM Product Description The YES 20 is a basic sash type storefront that supports monolithic glass. It can be center or flush glazed per project specifications. It is ideal for interior use that has minimal temperature changes. This system has longer horizontal mullions which results in greater spans for projects. With easy setup and installation, this system is ideal for office or interior store settings. The Glass size can be set with a variety of thicknesses that is as small as 3/16" all the way up to 1".