Size: Suitable for all 88/61/54/49/37 key pianos and keyboards. White key sticker 4.0cmX1.55cm(1.57X0.61). Black key sticker 3.9cmX0.85cm(1.54X0.33). Durable: The letters are printed on the backside of the transparent sticker, so they can withstand constant impact of fingers, will be always legible and never fade. Waterproof, when the surface is dirty, simply wipe it with a damp cloth to clean. No Glue Left: The adhesive on the backside is clean and durable, can be removed / pasted many times. Leaving no residue on piano keys, completely no harm to keyboard. Good Feeling: Piano key stickers are very thin and you can barely feel them when you play the piano. The sticker has a smooth surface and no resistance, making it comfortable when practicing techniques such as portamento and arpeggios. Easy to Read: The piano letters are large enough, clear, and easy to read, kids feel joyful to learn the piano and memorize note positions. Great for beginners and little masters.