Lie flat on a bench holding a dumbbell in each hand with your arms extended above your chest. Keeping your upper arms relatively still, bend your elbows to lower the dumbbells down toward the sides of your face. Pause briefly, then extend your elbows to raise the weights back up to the starting position in a controlled motion.
Log your dumbbell lying extension (across face) sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.