The Wall O Water Season Extender will add up to 8 weeks to your growing season. These are long lasting, reliable and completely made in the USA. Simply fill the tubes of these self-standing plant protectors with water and use them to protect your plants from early and late season frosts. They provide additional heat for plants so you can plant earlier and harvest later. Protects plants down to 16 F. Reusable. 18" diam. x 18" high.