On Cloudboom Strike Reviews

Worn for most of their workouts, at nearly all paces, and it felt comfortable and smooth. The thick foam insole makes the forefoot very bouncy, which suits 5K up to the half marathon; they are unsure about the end of a full marathon and think heel strikers will get less from it. Heel lockdown is weak, with some slipping and a worry about rubbing, and the very long laces came undone twice despite a double knot. The toe box is roomy and the outsole grips well.

A-/B+/A-. On's bounciest super shoe. One tester nearly made it his racer of the year except for the heel. Another tester loved it for a 10K but not longer. A third tester gave it an A for the bouncy, propulsive ride she'd missed since the Alphafly 1.

On's best race shoe yet: light (<8 oz), with Helion HF cushion right under the forefoot and grippy rubber. Sizing ran long by up to a full size, and the stiff heel collar dug into one tester's Achilles, leaving it unrunnable two days later. Wear crew socks. A Vaporfly 3 costs $100 less.

In their usual size, this runner gets heel lift in the On Cloudboom Strike even with a runner's knot.