Centering rings and bulkheads are essential parts when building a rocket from scratch.
You can use centering rings to space tubes within tubes, an example of this is mounting your motor tube(s) within your main air-frame. We sell pretty much any size - size centering ring, so if something is missing do let us know!
Bulk heads are great for gluing in to couplers to attach eye bolts. This is a good solution to attach your payload section to your main rocket tube for example.
Example: You want to mount 3x 18mm motor tubes within a BT-70 rocket air-frame. Pick the twin pack of BT70 - 3x 18MM. This comes in a "T" version and standard version. The T version has rectangle slots for engine hooks by the tube holes.