Standard KoolTray II The KOOLTRONIC KoolTray II delivers cooling air to hot spots by localizing fan placement to the heat generating area(s). With its 1¾-inch [44.5mm] single-U height it fits right under card racks or near heat-producing sources. Standard units are available in 1, 2, or 3 row models. 19-inch [482.6mm] unit width is standard. Smart KoolTray II In addition to specific cooling fan placement, the Smart KoolTray II provides two optional choices of component protection. The X5 option sends both a visual and external alarm in the event of fan failure or low fan speed. The X7 option varies the fan speed as temperature decreases or increases relative to the set point and sends an alarm for high temperature conditions. The X6 option combines both the X5 and X7 options.