This is a nice piece of equipment made by Sportsheets for the low price of only 31.99. If you were to buy the same product from an adult store, you're looking at a price tag of 39.95 + tax, and the gas getting to the store.
The set includes:
1 Hogtie steel O-ring that you connect the other 4 pieces
2 Wrist cuffs
2 Ankle cuffs

The large o-ring is made of smooth metal and has four separate points that the rest of the restraints can be hooked into. It's also compatible with most other restraints.

The restraints open and close with a buckle device. All of the straps are made from nylon. It's very strong and resilient. The material is great in basically all weather and will remain strong even after much use, making more play time for you at a cheap price. Not only are they weather resistant, but also hypo-allergenic, and they have a very good resistance to oils and greases. They're One size fits “most”... notice the "Most".

The nylon can be washed in warm soapy water. Do not use a scouring powder or anything harsh as it'll damage the material sooner than it should.
Since they connect to a metal ring, it can be separated from the straps and washed either in the dishwasher or with basic soap and water. The entire set is latex free and non-porous.

As for the safety issue, you just need to make sure nobody has any cuts or scrapes, as the restraints may soak up some blood in the event of open wounds even of the slightest nature, and use a wash cloth or a sock with each strap to protect against anything getting on or in the straps. As with any bondage, both light and hard core, the partner needs to make sure that the submissive one still has the ability to feel in both lower and higher extremities (business as usual), so the experience is pleasurable for both partners and not only for 1 with the other passed out somewhere. The restraints, if done behind your back, are impossible to remove yourself so your partner has to remove them for you. If done in front of you, then it's pretty easy to undo yourself once you get your hands free.

The wrist parts fit comfortably, and when pulled they didn't break or come undone. The ankle parts, however, just barely fit. I'd say that these would have to be altered in some way to make them fit correctly, or just save some points for a larger set of leg restraints to use with the hog-tie set.

Getting back to the "most" part statement: The wrist and ankle restraints are 9 3/4" without the Velcro straps locking on to the other side of the restraint to keep it in place. My ankles measure 11" so there's no fit whatsoever except by using the Velcro strap, but that chafes the skin that it touches. Also, before you buy you need to make sure that you can still get into the positions that these would put you in. Me being out of shape, I had to use another person with this one.

This does have the right idea, however the restraints need to be larger and the chain links need to be longer. Both of which would help with the larger population who are into BDSM and like to be restrained.