From A-20 prototype came the development of the A-32, which didn't use the wheel/track-option, but was now fitted with a short 76 mm gun. The A-32 prototype had proved very good in trials and a small production was delivered by the name T-32. However battle experience in the Spanish Civil War made it clear that it had insufficient (too thin) armor protection. After getting a thicker hull and other changes made it was called T-34 and should be the most famous tank of its time. (See this ).