Air frame couplers are used to join air frame tubes together. You can either glue both ends for a permanent solution, or glue just one end in so the tubes can come apart. You can also use couplers to strengthen air frame at points where necessary by gluing them down a tube.
You may also want to check out our transitions section as these can be used as couplers while simultaneously changing the tube diameters.
We've picked the most likely couplers for UKROC here, but there are more in the main coupler area on our website here.