A variation known as "Correcting Selectrics" introduced a correction feature, where a sticky tape in front of the carbon film ribbon could remove the black-powdered image of a typed character, eliminating the need for little bottles of white dab-on correction fluid and for hard erasers that could tear the paper. These machines also introduced selectable "pitch" so that the typewriter could be switched between pica type (10 characters per inch) and elite type (12 per inch), even within one document. Even so, all Selectrics were monospaced—each character and letterspace was allotted the same width on the page, from a capital "W" to a period. Although IBM had produced a successful typebar-based machine with five levels of proportional spacing, called the IBM Executive, proportional spacing was not provided with the Selectric typewriter or its successors the Selectric II and Selectric III.