Stethoscopes all look the same. Some have different color tubing, but these choices are limited. So, in the clinical setting, you need to somehow mark your own stethoscope in a way to make it stand out. Why not knit it a little sock? It will stay on, but is easily removable to wash.
Using sock yarn and size 2 DPN's, I cast on 12 stitches (the circumference of the scope, including the tubing is 1 and1/4 inches, I was aiming for 1 and 1/2 inches) and join in the round, being careful not to twist. For this little cover, work the first 5 rows in a seed stitch, work 10 rows in stockinette stitch, another 5 rows in seed stitch, then 10 rows in stockinette stitch, and end with 5 rows of seed stitch. Bind off while working the last row. The finished length is 3 and 1/4 inch. I am not sure of the amount of yarn used, I will measure for it soon and edit this post, but it's just a small amount of scrap sock yarn.
Now you have something to make with all of those little balls of leftover sock yarn. It will make a thoughtful gift for someone you love who uses a stethoscope!