Earth Spas Corner Pillow.
 
There is two styles of pillows which fit the Earth Spa Hot Tub range, this is the less common of the two options. 
 
Length: 300 mm Width: 120 mm Distance Between Screws: 140 mm
 
Fits Earth Spas Series Mariana, Glencoe and Ha Long Bay
 
Price is for a single pillow.