These bolster covers come in four sizes to fit a wide range of bolsters. 
The 1/2 Round Cover fits bolsters of approximately 3" x 26" in size.
The Full Round Cover fits bolsters of approximately 6" x 26" in size.
The Half Jumbo Cover fits bolsters of approximately 4 1/2" x 26" in size.
The Jumbo Cover fits bolsters of approximately 9" x 26" in size.