It looks good and a little like a upmarket version of the Rojak Ladder Stopper.
You won't find any British Standard Kite Marks on any of the ladder stabilisation devices. I'm not sure what the reason for this is.
Maybe they won't test them, because if someone falls using one, then the testing agency would be liable for prosecution.
However, they do work.
I used to use my Rojak for those 'dodgy windows' and once they slipped.
Unlike a ladder, which when slips causes a 'catostophic failure', the Rojak is capable of 'slipping and stopping'. It gave me enough time to steady myself and gingerly climb down the ladder.
An 18" Rojak will comfortably fit on top of a large Unger Bucket, so it's fairly easy to carry with you too; heavy(ish) though.
Ladder matts are also an excellent bit of kit for uneven surfaces.