Barrel is the general name which rappresents different types of this equipment depending on the curved shape and size of the semicircular part. the different tools rappresenting this family are: Small Barrel, Step Barrel or Spine Corrector or Half Barrel, Large Barrel or Big Barrel.
The big Barrel or Barrel as insiders like to name it is a training tool made of a vertical structure with wooden bars and padded wooden semicircular part which reminds the form of a lying barrel. It is to note that the Large Barrel has its semicircular part set on a stainless steel "L"-forming structure. The vertical part of this structure resembles a wall bar. The Large Barrel has the biggest dimension with respect to the semicircular part.