Mason Bee Nesting Tubes are cardboard nesting tubes are attractive to mason bees and are an inexpensive way of getting started. The 35 tubes are closed at one end to provide the ideal mason bee nesting conditions. When it's time to clean the cocoons, the tubes are moistened and gently peeled apart. These are good replacements for the Starter Cottage and Tube Holder Kits. This item is 7cm wide, 7cm tall, and 16cm long.