Top 4˝ of grow tube are open to allow for greater ventilation while also keeping the base of the plant completely protected. SHELLT® Grow Tubes provide protection to help young plants get established and grow faster, saving both time and money. The hinge and locking mechanism makes them very easy to open and close with no need for ties or tools. Plus, units can be easily combined to create a wider or taller grow-tube. Made of robust and recyclable plastic with UV inhibitors for many years of use. Easy to open and close with two clicks. Easily removable without damage to the plant.