Each arm has exactly one inch of sleeve room for the inserted pipe. You have the option of either gluing the pipes into the hub connectors or securing them with nuts and bolts.
Stainless Steel nuts and bolts are included in both the Basic Kits and the Full Kits. It is necessary to specify which pipe size you are planning to use (1" or 1 1/2") so that we can include the correct size bolts.
The hubs themselves are made of high-strength white PVC, with pre-molded holes for bolt fasteners placed 1/2" from the end of each arm. There is a 12-degree curvature molded into each arm from the hub center, which gives the hubs an 'inside' and an 'outside' when putting the dome together.