This microphone was commercialized in late 1933 as the RCA 77A Unidirectional Microphone. The microphone was an instant success. The RCA 77A was followed by the RCA 77B, 77C, 77D and finally the 77DX. The 77A was a huge mike which had a rounded top and a flat bottom. The 77B and the following models were much reduced in size due to stronger magnetic material available at the time. All of the 77 models used a rubber shock-absorber in the stand mounting connector.