We first started using GEM about 17 years ago when we had to replace the screen door at the side of our house. We have an old house, almost 100 years old, and nothing is standard sized. I called around to various places and the only company that was helpful and happy to provide and install a custom-sized screen door was GEM.
We have since replaced almost all our windows (over the years, a few at a time) with GEM, including a back patio door that was oversized, not standard. We recently used GEM again to replace our front door as well as our front hallway windows, and 2 other windows in bedrooms. The GEM salesperson listened to what we wanted, made some suggestions that fit our budget but would still give us the effect we wanted, and everything followed from there. The installers are very neat and clean up thoroughly after themselves which we (and our neighbours) appreciated. The door and windows look amazing.