We commonly use a Rancho sliding window but there are many options available.  We work with a variety of vendors that offer other options including vinyl and commercial quality windows in all sizes and configurations.  As for other sizes, some very common sizes are the 4030 (4'x3'), 3040 (3'x4'), or 3030 (3'x3').  No matter what size you are looking for, we can help you find the right fit for your new building.