Holds 35 tubes. The Blue Orchard Mason Bee, technically known as Osmia lignaria, is an excellent pollinator. Each one can do as much pollinating as 120 honey bees. This kit will help attract these beneficial bees to your garden. Since Mason Bees are solitary bees and do not make hives, they are always looking for a place to make a home. They look for a hole or tunnel that has been bored out by a beetle or other insect and go in and clean it out. When they find these tubes that are the perfect size and shape, and already cleaned out, they will move right in! Includes nest with 35 tubes and mounting bracket.