I used a pen and struggled to write at the very begginning

Note that you'll need to have a good pen with permanent ink, like a fine-tip Sharpie, so make sure to pack one

I guess if they sold these with the correct pen they would be terrific.

Use a good, preferably permanent pen to write on it

; no clue given as to what pen works best on this.it does fit children well and seems near impossible to remove until one uses scissors to remove it.