UKH

The boy has now outgrown his kids full harness, needs a new harness then - tried on my waist harness and it is way too big for him round the waist (cough) - which harness for a teenager then?

(or do I just do the slings round his waits/legs until he has grown into an adult harness - joke)

One of these did the job for us at that stage

https://www.gooutdoors.co.uk/15906608/black-diamond-kids-momentum-harness-1...

I would go to a shop with a good selection to try on. Quite a number of kids harnesses on the market, even consider trying women's ones too for comparison. Just try loads until you find one which fits well

Spent Saturday climbing with the kids.

Found my Wild Country Synchro size small will go down just about small enough for a 10yo, so should cover a teenager to adult.

Perfect, thanks - who'd have thunk it - a kids specific harness - whatever next!

(saves me a 50 mile round trip to climbing shop to find out they only stock adult size harnesses)

There are quite a few kid-specific sit harnesses (we've got an Edelrid Finn - see also Mammut kids Ophir, DMM Tomcat, Petzl Macchu, Simond Kids Easy and so on), but check the waist size range carefully, as you said "teenager", which would suggest he'll probably be at the very top end of the size range, if not too big, for these and a small adult harness will probably be a better long-term purchase.

Women's harnesses have a longer waist-crotch drop than men's harnesses, which can mean the waist gets pulled uncomfortably high around the ribs on men in a fall.

I'm not saying don't, just be aware.