Whilst it's a nice product, it didn't fit either of my aluminium ladders, so I think the "Fits into the hollow rung of most modern aluminium ladders" claim needs to be revised (2nd bullet point in the main description). I wish I'd noticed the review by "THOMASIO" on 5 Aug 2017 as this highlighted the issue! One of my ladders has 18mm diameter rung holes, and the other has d-shaped 17x28mm holes.
I'll be returning this as it's no use to me - I'll also ask ÍøÆغÚÁÏ to get the description revised as I expect they'll be having a few returns...