61 keys: Ideal for compact keyboards, synthesizers, and home keyboards (organs) with 5 octaves. Covers standard portable learning instruments and MIDI controllers.
73 keys: Designed for stage pianos and vintage-style keyboards (such as electric pianos/Hammond) with 6 octaves. Offers a precise fit without excess fabric.
76 keys: Suitable for medium-sized stage pianos, workstations, and slightly larger keyboards. Elastic covers in this category often also fit 73-key instruments.
88 keys: For full-size keyboards, digital pianos, and classic electric pianos with 7 octaves. Covers the full length of a standard piano.
