Top American coach Topher Boardeau has written a review of the Drehe4r Aero sculls forthe US rowing magazine, Rowing News.
Two things affect the speed of rowers and their equipment: propulsion and drag. And while there's only one source of propulsion, drag comes from two places: the water through wich you propel your shell, and the air moved by you and everything not in the water. The faster you go, the greater the drag. And while shells have always been designed to reduce the drag of water on the hull, few products have sought to increase aerodynamic efficiency.
Dreher's DreherAero sculls utilize the same design trick to get more aerodynamically friendly and increase propulsive force. The secret is a shaft and blade design manufactured in a continuous shape that makes the oar less visible to the wind on the recovery and lets it grip the water better on the drive. It's reminiscent of the cycling industry's early attempts at aerodynamic shapes, when vertically bladed frame designs made bikes invisible to headwinds but tough to handle in crosswinds.