These cuffs have soft nylon interiors that feel almost like a cross between velvet and flannel with sturdy nylon cord on the exterior. They are held together with a sturdy plastic buckle and fasten with Velcro. They will fit a wide variety of wrists very well from my tiny tiny ones to big manly ones.
They are again, quite sturdy and held up well against my valiant struggling, of course as they are handcuff style restraints all you really have to do is reach over and pull up the Velcro strip on the other cuff to get free (as your hands will be close together) but this is nice in a beginner bondage cuff as it allows for the idea of helplessness (standing up to struggling) without actually making the subject helpless.
The only quibble is that these are less than beautiful, looking more like a piece of camping gear than a sex toy.
These performed admirably: they are sturdy, well designed and well made. They can take a LOT (and I do mean a LOT) of struggling, and remain secure and comfortable. They will chafe delicate skin a bit if you struggle a lot, but most materials do. They're soft and easy to escape but not flimsy, making them non-threatening and sturdy (sturdiness is a trait unfortunately lacking in many lighter bondage cuffs).
All in all, they're admirable beginner/light bondage cuffs.
Hand wash and don't put them in the dryer or you'll melt the plastic.
These come in a plastic bag in a cardboard box with minimal instructions, however they really don't need much in the way of instructions.