3M Magic Tape, Code 811, 0.5in. (12.5 mm) x 36 yds. (32.9 m) long

This tape is truly "magic". Translucent on the roll but it becomes quite transparent when pressed firmly down on any flat surface. But that is not all of its "magic". Unlike other tapes, you can write on this tape with a ball point pen. It is therefore ideal for tape-labeling sample vials, sample bags, even glass slides. Just pull off a piece from the roll, stick it down on any firm flat surface and write!

We have also found that there is good resistance to water challenge but there is no resistance to common laboratory solvents. 

Dimensions: 1/2" wide x 36 yards long (12.5 mm x 32.9 meters).