I bought this monofin for my 10 year old daughter. It is an amazing fin and she loves swimming with it. It was the perfect length but unfortunately it feels like her foot is being crushed and she can only use it for a short time. We purchased the sock, but the sock only covered her toes and we didn’t think it was any use. We are looking to get a full sock as this may help. I’ve read a lot on the tightness of the fins and how to mould them to feet, but I think the fin is just slightly too tight. We are very happy with the fin and glad we purchased it as she swims like a fish and loves it