AA Car Essentials Reflective Vest Family Pack - set of 4 hi-vis vests.
Seems like a very good price, and as far as I know it wasn't a clearance or reduced offer (just a normal white shelf label), so should be available in most Tescos - found this in Doncaster Balby Tesco Extra and there were plenty amongthe car accessories.
In some EU countries it's mandatory to carry hi-vis clothing in your car, and even if you're not going overseas, for a quid each they're a pretty good buy for cyclists or just to keep in the car for emergencies.
Comprises 2 adult & 2 kids
Adult are both XL - labelled 96-132 chest, 164-198 height. I'd say they'd fit pretty much any adult, even if you're really big you don't need to fasten it up as they're waistcoat style with velcro fastening.
Kids are both the same size, to fit 80cm-150cm height, 48-84 chest. I'd say that these would fit from about 3-10yrs comfortably.
Bright yellow with lots of reflective stripes on them.
Conforms to EN471 and exceeds EN1150.
Can't find these on Tesco Direct, so assuming it's instore only. Found the same item on speeding.co.uk for £12.99 so defo a bargain!