A very small and useful accessory, particularly when taking landscapes using a tripod (especially the ubiquitous mini versions).
I had one of these in my bag for years until it ultimately went missing. Everytime I went to use it, I nagged myself to get a new one and promptly forgot.
Eventually, I spotted these on Amazon and at such a low price, I ordered (expecting them to be inferior quality junk).
I was pleasantly surprised to discover they are just as good as my old Jessops version (and having two is great - one for each gadget bag).