The "F" Style 1/2" to 1/4" branch fittings are a convenient alternative to
"Y" and "T" connectors. They are used to link two water-blocks in parallel using
dissimilar tubing sizes. The F fittings are made of POM (Acetal Copolymer).
The advantages of these barb fittings compared to Y's or T's are: Cleaner
routing of the tubing, reduction from "large" tubing size such as 1/2" or 3/8"
to devices installed in space constrained areas and necessarily requiring 1/4"
ports & minimal pressure drop.