ModelsB-Models are stretched out of .060 aircraft aluminum and heat treated to T-6. The do not have ribs. This allows for flexibility when going over rocks or logs in the water.
T-Models are stretched out of .050 aircraft aluminum and are heat treated like the B-Models. They have stretched-in sponsons which add strength and stability. T-Models also have extra ribs (4 on the T-15 and 5 on the T-16/T-17 models).
L-Models are stretched out of .040 aircraft aluminum and are heat treated. This model comes with three ribs in each of the models. The L-15 and L-17 have stretched-in sponsons, while the L-12 and L-13 have smooth sides.