I have just recieved my order of this 4 pack of A4 notebooks. Unlike the picture for this item, the books are all full of 4-hole punched sheets. On seeing the image here I was worried that I might have to buy some US imported 3-hole files, or put each sheet in a plastic pouch, but instead I can use my standard UK/european 2-hole ring binders as ever.
These notebooks have 80 sheets, not 100 as written in a couple of comments. Actually, sides 1 and 160 are backed by special pages printed with basic pen controls, so that's 79 double-sided sheets plus these two odd ones. Each lined page has a huge ~4cm tall area above the top line, which could be an irritating waste of space or a handy doodle area, depending on viewpoint.
The books are really heavy for the number of sheets, partly through being high quality but partly because they each contain a large doubled cardboard 'divider' with a pocket on each side. I haven't worked out how this is meant to be used yet -it isn't neatly detachable from the book, unlike the perforated paper sheets.