After the New Year, our streets were littered with burnt out fireworks and rockets. as were yours I expect. My wife wanted some 5 or 6 mm sticks for a Craft Project and we went out collecting. We found that there were basically two sizes, about 2 feet long and 5 mm square and slightly longer and 6mm. Nearly all were straight, and most were basically un marked. Suprise, suprise there were some of Balsa Wood among them, the others being pine or fir. I now have a usefull supply of Strip, for internal rails, servo Mounts etc, also the street is tidier! ( the wife is happy too and I have saved a 40mile round trip to our nearest model shop.)