Adding fins to rocket airframes is tricky. You want to get them on accurately for the sake of your flight characteristics. This short kit can be used, in conjunction with some cheap and available parts, to build a jig that will enable you to add fins perfectly vertically and on the centre line of any rocket with a diameter between 13mm and 80mm. So the kit JUST includes the lasercut 6mm thick MDF parts and you'll need to add some M5 threaded rod and nuts, some thin shock chord, some M4 nuts and bolts and some cheap angle aluminium angle stock, all should be available at your local hardware store.

The MDF parts are designed so that they instantly make an accurate jig and the metal parts you add don't have to be made to any great accuracy. It's tricky to show how this jig works in just a couple of pictures so I've made this video below that walks through how to use the jig and also how to build one. I can't emphasise enough how much I've used my own jig since I made it in 2018, it really works well and I've made a couple of refinements to this short kit so that it's even easier to build.