PENpal Sticky Labels are compatible with all PENpal devices. Each set comes with labels in three sizes: small circles, big circles, and big squares. The size of the label makes no difference to how mauch you can record onto it. There are 381 stickers in one set (54 big circles, 54 big squares, 273 small circles). 
 
Sticky Labels come in sets from A to J. At this point only set A is available, but more sets will be available next month. 
 
To learn more about working with PENpal and Sticky Labels read this post:  https://www.montenglish.com/post/penpal-a-device-which-will-change-the-way-your-students-learn