Great product for aligning fins. Always put the motor mount in first when using the jig.

This is my 3rd Fin Alignment Guide from Estes and is perfect for your average size model rocket, but is kind of tight on BT-80 body tubes and to small for there old BT-101 body tubes. It can also be used for aligning launch lugs and external body tubes on the main airframe. Excellent jig for 13-54mm motor mounts. Hint: Use cellophane tape, like Saran Wrap on the fin guides and the glue does not stick. For a more sturdy mount, be careful tightening the base down, with panhead screws, it will crack if over torqued. If the fin jig gets loose you can shim it with white plumbers Teflon tape and it won't bind.