Here is a short page on mason bees. It shows some tubes, nesting box, and cocoons. http://www.bjornapiaries.com/masonbees.html
We ship in winter, the bees hatch in time for the apple blossoms, and last 4-8 weeks. Right now, the masons are about finshed for the season.
Regardless of who you order from, buy the tubes with paper inserts. Do not buy wooden blocks with holes drilled in them. You need a system which will allow you to clean cocoons if you choose to do so.