"The banks of cathode ray tubes, similar in principle to television tubes, were the heart of the IBM 701 Data Processing System. They gave the machine much of it's tremendous speed and flexibility. The 72 cathode ray tubes in the Electrostatic Storage Unit could store 10,240 digits, any of which could be obtained for processing at other points of the machine in 12 microseconds. The Model 1 of the 706 accommodated 2,048 full words of 36 bits or 4,096 half words of 18 bits. A maximum of 4,096 full words of 36 bits or 8,192 half words were available when both the Models 1 and 2 were installed.
"The principal advantages of Electrostatic Storage was the short time required to refer to information at any given location and send it to the computing unit, and the random access to any 706 location afforded the programmer.
"The Model 1 had a monthly rental charge of approximately $2,600, and the Model 2 was rented at $3,500 a month. Customers could specify the IBM 737 Magnetic Core Storage Unit in lieu of the 706 at a monthly charge of $6,100" (https://www.ibm.com/ibm/history/exhibits/701/701_1415bx06.html).