T cells and B cells differ in the form of the antigen they recognize, and this affects which antigens they can detect. B cells bind to antigen on invaders that are found in circulation outside the cells of the body, while T cells detect only invaders that have somehow entered the cells of the body.
ABS, DWV, Solid or Cell Core sewer pipe. The solid pipe is composed of ABS at 99% while the cell core is composed of a cellular foam between 2 layers of ABS which makes the cell core pipe lighter.
What you have is not solid. There's a foam or cellular interior to the pipe with two thin layers of sold ABS on the outside. 1  It costs less and weighs less than solid pipe. 2  Thus it's popular at home stores that compete on price. 3  Not every jurisdiction allows use of cellular pipe. 4  However it's common in the USA.