Starting in 1981, Tandy Radio Shack released a number of different hard drives for their popular line of microcomputers. The first one to be released was the 8 MB Hard Disk Drive for the TRS-80 Model II. This unit contained an 8″ Shugart SA1000 hard drive bubble along with an 8×300 based controller board. With the subsequent industry introduction of the smaller 5 1/4″ MFM hard drive bubbles, the next hard drive unit released was the much smaller 5 MB Hard Disk for the TRS-80 Model I and III and a similar 12 MB Hard Disk for the TRS-80 Model II and 16. Future updates included the 15 MB, 35 MB and 70 MB units which were all sold for the Model II/12/16/16B/6000 line of business computers.