Astron Midget (K-40) upscaled to use standard 18mm motors. This uses Semroc ST-16 for the upper stage and Semroc LT-114 for the booster stage. It has motor mounts to accommodate standard-length 18mm black powder motors in both stages, in contrast to the original Astron Midget, which utlized that shorter Series III motors. Another change is that this upscale uses gap-staging to ignite the sustainer, instead of direct staging as in the original model.

This upscale is based on the original K-40 Astron Midget (released in 1969), and not the later TK-40 Mini Brute Midget, first released in 1972. I keep trying to specify that in this rocket's data, but the rocketreviews.com website keeps changing the field to say that this is a Mini Brute Midget. The TK-40 Mini Brute Midget had different dimensions and tube sizes, and would have required a different scale factor in order to yield this rocket.