Antique book keycaps are slightly oversize and should be installed on mechanical keyboards with switches that are not inset in a case. They may also rub against adjacent keycaps, so they are recommended for use as ESC keys.
Book keycaps are individually handcrafted. Keycaps are for mechanical keyboards with Cherry MX (or clone) switches. Every keycap is slightly different, and may have small imperfections. By purchasing, you agree to buy as-is.