Estes Fin Alignment Guide for Gluing Model Rocket Fins (002231)Fast & accurate fin alignment for three or four finned rockets Fits body tubes ranging from BT 20 to BT 80 Can accommodate either 3 32 in. or 1 8 in. balsa, bass, or plywood fins Easy to follow instructions are included No more guessing where your balsa fins go, this guide does it all for you! NOTE: Color may vary. Body tubes and wood not included. A precision molded accessory that makes it easy to glue three or four fins to various sized body tubes