Sure it contains some parenchyma, but the rest is sclerenchyma. Some of that sclerenchyma is fiber which does not conduct. The remainder, however, is all conductive. The earliest matured tracheids have annular, spiral, or reticulate wall thickenings. Later-maturing tracheids have pitted walls.
Vessels are also thick-walled, dead, hollow cells, but lack end walls.
They are typically much larger in diameter and are therefore major pipes in the plumbing for water movement. The wall thickenings in vessels are pitted. Xylem functions in the transport of minerals from the soil up the plant. Phloem Phloem is basically a parenchyma tissue. Sieve elements are living cells with typical thin walls.