Listed charm sizes include about 53 mm × 32 mm and 48 mm × 104 mm, with a 30 mm keyring noted. Some listings also give overall dimensions in inches such as 1.0" × 6.0" and 3.2" × 1.5".

Suggested ages shown in the listings are mainly 3–10 years and 4–10 years.

Several keyboards include learning modes with illuminated keys or red-light guidance to indicate the next note, plus demo melodies and guided light-up key play.

Some listings mention Aux-in or Line-in connections and state that an MP3 player can be connected for playback and recording.