It used to be that hoof gloves (or hoof mitts as they are sometimes called) were a fairly specialized piece of equipment available only from a few dedicated ponyplay retailers, but in the last few years I have seen molded rubber fist mitts become widely available from many BDSM retailers (the bottom of this page contains a partial list of retailers from which you can buy them). I'll be reviewing the Fetisso brand hoof mitts that are stocked and sold by several retailers.
I think it is great that they are so easily accessible. Hooves are a cool piece of tack to have, and the fact that they are easy to obtain and can be added to a pony's tack collection with relatively minimal expense (compared to, say, hoof boots) is a great thing for ponies looking to augment their tack collection. If you are not familiar with these, the photo below shows the rubber hoof mitts I will be reviewing here.
I purchased my first pair from Madame-S several years ago (I'm not sure if they still sell it on their website, but they did have a bunch of them in-store last time I was there ~ 2010). Since then, I have bought a few new pairs, one more from Madame-S, and the rest from different places. Most retailers sell the Fetisso brand, so when looking to buy, you should only have to worry about price, and availability (some places do not stock all sizes), but you might want to check with the retailer before purchasing as other brand hoof mitts have been reported to use thin rubber that tears easily.
These hoof gloves are meant to fit quite snugly around the lower arm, so when sizing you should take this into account. I find that it is more important to size for your lower arm than for your hand. When sized properly, they will keep the wearer's hand in a somewhat loose fist.
Since the rubber can stretch, most people will be able to (almost) open their hand flat inside the hoof if they really try. However, it requires a fair amount of effort to do so and it is very difficult to keep your hands partially opened for any amount of time. Thus, I would consider this almost a fist mitt. Moreover, the rubber on the bottom of the hoof is much thicker on the "horseshoe" shape, which makes it nearly impossible to use your hands when wearing this hoof mitt.
Due to the elasticity of the rubber, it is actually not that difficult to put on one of these hooves though you will probably need to use a little lubrication. However, once you have one on, it is quite difficult to put the second on without another person's help (not impossible, but you will usually at least need a doorknob or something to help stretch open the top of the glove).
Once you put the hoof mitts on, you will find them to be comfortable. As I mentioned above, the mitts will encourage you to keep your hand in a fist, but you can occasionally stretch them out if need be (albeit only briefly and requiring a bit of effort), which makes them much easier to wear for extended periods of time.
The only complaint I have when wearing these (and this applies to any fist mitts) for an extended period of time (e.g. overnight) is that my knuckles become quite sore. I have the same problem in padded leather fist mitts, so it is not a complaint specific to these hoof gloves. Moreover, this only happens when I wear them for a long time.
If you have these hoof mitts on both hands, it is quite difficult to get them off using only your mouth or other (hoof glove encased) hand. However, if you used lubrication (or have worn them long enough that your hands have sweated a decent amount) they are relatively easily removed by putting your arm between your legs and using your legs like a vice to grip the hoof gloove while you pull your hand directly up and out.
Thus, if you want to make sure the hoof mitts stay in place, you will have to use wrist cuffs over top of them. Again, though, if the wearer's hands are slick enough (from sweat or lube), it will usually still be possible for him to use his legs and pull the mitts off. This can be prevented by restraining the wearer's arms in such away as to prevent him from positioning the hoof mitts between two objects in an attempt to pull his hand out.
Overall, I really like these hoof gloves and have found them to be durable and low maintainence. Over time the rubber will stretch and it might be necessary to replace them though it takes a lot of use for this to become a problem.
When wearing the hoof mitts, I feel deliciously helpless. It is really amazing how helpless you feel just loosing the use of your fingers. Not having your hands restrained but still being rendered somewhat helplessness to perform many tasks adds a big psychological element to the bondage, which I especially like. Plus, it's a trip to look down at your hands but see hooves instead.
You can find these molded rubber hoof gloves/hoof mitts from several different retailers. I have split the retailers into two lists. The first list is of those who (as far as I know, but check before you buy if this is important to you) sell the Fetisso brand, which tends to be of a thicker rubber, and the second list of those who sell a different or in-house brand.
Fetish-Pets-Store - €97.50 EUR + shipping. Available in small, medium, and large in your choice of black, red, or transparent latex. Although the hooves are still available in red or transparent color from Fetish Pets, these colors cannot be selected as part of the ordering process. Instead, you will have to specifically ask for those colors by including a note when you place your order (data from 2017-10-21). Best Price
Fetish Universe - €99.90 EUR + shipping. Available in x-small, small, medium, large, and x-large (data from 2017-10-21). If you are not in EU (e.g. U.S.), ask them to remove the 19% VAT.
Leder Gummi Studio - €100.67 EUR + shipping. Offered in black only. Available in small, medium, and large (data from 2017-10-21).
Bizarre Rubber Shop - €109.95 EUR + shipping. Their site says they offer these hooves in black rubber only. Available in small, medium, and large (data from 2017-10-21).
Blackstyle - €119.00 EUR + shipping. Available in small, medium, and large (data from 2017-10-21).
Fetish Shop - €155.00 EUR + shipping. Available in small, medium, and large. No longer available in red or transparent rubber, only in black. From reading the description, it sounds like 19% VAT is already included in the price, so U.S. customers should be able to get them for about €118.50 EUR, though make sure to check with them before ordering (data from 2017-10-21).
The Stockroom - $179 USD + shipping. Available in medium, and large only (data from 2017-10-21).
Fetish Zone - $189.95 USD + shipping. Available in medium and large (data from 2017-10-21).
Fetisso Wholesale - Catalog number 1550 are the hoof mitts. I believe they sell only in bulk.
Birch Place Shop- £42.89 + shipping. Available in one size only. These are made from PVC with a zipper entry. They are available in black, red, white, pink, blue, and purple. They have a slightly different look from the Fetisso brand but are placed at a much nicer price point (data from 2017-09-21).
Polymorphe - $86.00 CAD + shipping. Available in two sizes: S-M (Wrist 6", Forearm 8") and L-XL (Wrist 7", Forearm 9"). By far they are the cheapest of all retailers I have come across for pony hoof gloves, but I believe they use a thinner rubber than the Fetisso's. Edit: Sadly, they have discontinued making their hoof mitts, which is rather unfortunate since they were a nice and affordable option.