Material: Durable stainless steel, can be used repeatedly for a long time. It is recommended to wear gloves when using this soil blocker to prevent hands from being scratched. Better For Seedling - The soil block produced by soil blocker minimizes damage to fragile root systems during transplanting and avoid root binding as the roots are air pruned when they reach the edge. Part of the unique Micro / Mini / Maxi "nesting system" for starting seeds and transplanting starts. (Mini 4, Micro 20, and Cubic Inserts sold separately.) Essential organic gardening product; easy to use, and re-useable for years. This eco-friendly systems saves on plastic pots.