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.
The run pipe which having a branch(es) connection is weakened by the opening made onto it. The branch connection must reinforce the opening and restore the original strength of the run pipe. The intent of an Olet is to restore the header pipe to full strength when correctly installed.