fret strips are made of silicone, attaching the tabs without having to stick the fret to the keys. Feel free to remove them without leaving nasty glue stains.[Easy Identification] There is a double pentatonic display of the notes of each key, which helps to identify the corresponding keys faster.[Release and use] You can remove the note strips easily when you are familiar with the keys and note rules. If you are not so skilled, you can still put it back.[88 Keys Standard Size] For standard size 88 keys piano, you can easily use it on grand piano, upright piano, 88 keys digital piano, practice piano[Note] Not compatible with some non-standard 61/54/49/37 keys keyboard instruments, you need to confirm the size of your keyboard. The width of the gap between the top of the black keys and the keyboard shell must be wider than 0.2in(5mm).[For Digital Pianos] As many digital pianos have the black keys and the case attached together, so when you use this product there will be a problem of not being able to lay it flat, you will need to cut the connection off and use it, please choose carefully.