The light tracks are directional to allow the light to run the length or the width of the domes， allowing two trays to run side by side. Two vents in the top of the dome can be opened or closed to control humidity. Vertical sides allow the use of all plant sites in a propagation tray. Dual vents let you easily adjust moisture and humidity Clear - allows for light to prenetrate to reach your plants 7-inch-tall vertical sides for use with propagation trays Molded from extra-clear Plastic (Frame); Siding Material: Polycarbonate Plastic Imported Your security is our number one concern