The SX45 horizontal sliding window from EFCO, a Pella Co., is part of the company’s XTherm line of high-performance thermal products. The window can accommodate triple-glazing and can achieve thermal U-factors as low as 0.24 with an AW70 structural rating. The XTherm line also includes projected windows, a double hung window, a fixed window, and a curtainwall with triple-glaze capabilities. It is designed for new and retrofit commercial applications, including storefronts and entry systems.