Some companies have made their Bolsters Pillows and, therefore, their Bolster Pillowcases narrower over the years, however Linen Cupboard Bolsters and bolster pillowcases remain full size top to bottom, just like a standard size pillow but longer.
Don't be confused by high thread count.
May 17-Jun 6 Requested these covers to be made for a slightly different shape bolster and they are exactly what I wanted.
Very large bolsters are often used as hugging pillows, and a person may sleep with a leg and arm draped over one, taking the stress off of those body parts.