Basswood is a good alternative to balsa to use as fins for model rockets.

A domestic wood cut in Northern Michigan and Wisconsin, basswood is desired because of its economy, workability and finishing qualities. Its close, tight homogeneous grain structure makes it ideal for a wide variety of hobby and craft and projects. It is smoother and easier to finish than balsa.

Thin basswood, such as these 1/8" thick sheets, may be cut with a hobby knife; thicker basswood requires a saw for cutting.

This is a package of three (3) sheets of basswood.  Each sheet is 24-inches long, 3 inches wide, and 0.1250 inches thick.