2" slip is designed to slip over pipe with 2" inside dimension or 2" spigot.
2" spigot is the same dimensions as pipe with 2" inside dimension. Fits into 2" slip.
6 - 3/4" Smooth Barbed Ports are designed to fit inside 3/4" clear tubing or flex pipe
Manifold must be glued into place
Gluing tubing onto smooth barbed ports is a highly recommended method, along with clamping, when using clear tubing. With flex pipes, clamps are not needed.
Unneeded ports can be plugged with 3/4" new style manifold plug, sold separately.