Mason Bees are excellent pollinators. They have a pollination success rate of 93% to 98% compared to honey bees that have a 3% pollination success rate. The bees do not have a queen to protect so they won’t attack if they are disturbed. This is a much better choice for the backyard garden especially if children are around.14" tall x 5.25" x 3.75" with 5/16" holes.