Scalable Linear Recording is the name used by Tandberg Data for its line of QIC based tape drives.
The earliest SLR drive, the SLR1, has a capacity of 250 MB, while the latest drive, the SLR140, has a capacity of 70 GB. The term SLR is now often used to refer to QIC tapes, as they are the only drives still manufactured that use them.
Quarter inch formats
NOTE: MLR stands for Multi-channel Linear Recording.
References
Scalable Linear Recording Wikipedia(Text) CC BY-SA