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How should the Flex Hoof Boot shell fit the hoof?

You're about to purchase hoof boots for your horse, but the boot market is a jungle and you want to make sure that you don't waste time and money on purchasing the wrong boots.

Or you've bought your Flex Boots, but are now having some fitting issues and wondering if they're suitable for your horse? We're here to help!


"Does the shell have to be a neat fit right up against the hoof wall,

all the way around the top of the shell, or is it OK to have a bit of a gap?"

~ ~ ~

"Will the boots suit my horse that has narrow feet?"

~ ~ ~

"What if the hoof angle is shallower than the boot angle, even with a pad to lift the hoof - can that work, or not?"

~ ~ ~

"The hoof has a scar from an old crack that causes a dip in the hoof wall –

would the boots be ok in that situation?"


These are questions that people ask fairly often, so in this blog post Minna talks about common fitting issues and when Flex Boots can be made to work for your horse, as well as when they might not be suitable.

Narrow hooves

If the hoof is very narrow, there can be some space on the sides and this is still ok. From our experience, hooves that are a maximum of 10mm longer that wide, still work well in Flex Boots. We don't recommend Flex Boots for extremely narrow feet (where the length measurement is over 10mm more than width measurement), as the boot can twist.

Usually, if the hoof is more than 10mm longer than wide, there are some trimming issues that should be addressed. Soles can and do stretch forwards if they are consistently trimmed wrong, and understanding the hoof anatomy and where things should be, is necessary to correct such problems. A sad truth is that we see overly long hooves almost daily, where the owner is told by their hoof care professional that there's nothing wrong with the hooves, although it's obvious that the hoof has morphologies that are detrimental to the horse in the long term. The way around this is for the owners to learn to recognise a healthy hoof vs. a hoof with morphologies, so that they can make informed, smart decisions for their horse. We teach the basics of this on our Read Your Horse's Hoof course, which you can find here. With code SH23 you can get this course COMPLETELY FREE - because our passion is to help you learn!

Here is one example of a hoof that was too oval and long front to back. Over 9 months or so, the hoof became a rounder shape with a different trim on a shorter trimming cycle. In the after photo, the hoof shape is much more anatomically correct.

Upright hooves

If the hoof is very upright (and assuming it is perfectly trimmed), it is possible that the boot shell top edge is tight, but at the bottom near the toes there is a gap. This is undesirable because the toes will sit on the waves of the boot sole instead of the solid rubber part, and it can affect how well the boots wear and stay on.

In some instances, heat fitting can solve this issue, IF the feet are perfectly trimmed and the issue truly is a very upright hoof conformation and not excessively high heels that can be fixed with a trim. Heat modification should be done with careful consideration though, as any modification voids the warranty. If the feet are well trimmed and the correct size is selected, many of the more upright feet work very well in Flex Boots as is.

It's also worth pointing out here that our wide style Flex Boots are slightly more upright that the standard Flex Boots. So if your horse's hooves are upright AND fairly round in shape, then our wide boots might fit well.

Check out our blog post What kind of hoof shapes do flex boots fit for some examples of upright hooves that fit Flex Boots without any modifications.

Give it time

Sometimes all you need to do to improve the fit is wait; with use, the boots will soften more and take the shape of the hoof they're used on, so they kind of become one with the hoof. Whilst they don’t need breaking in, we find they get even better with use!

The red boot is brand new, and the green one is the same boot one year later. The initial fit was a bit snug at the back but the boot has molded to the hoof really nicely and is like a comfy sneaker.

Air gap in the middle of boot shell

An air gap in the middle of the boot shell indicates a flared hoof. This can affect the boots' ability to stay on, and we advocate for the horse to come first; hooves to be rehabbed first, then booted for riding after. As therapy boots they are amazing and the fit can be "off" a bit, yet the boots still serve their purpose to offer extra protection for the rehab hooves.

You can tell if there's an air gap by simply pressing down on the boot shell when it's on. The shell should hug the hoof wall evenly all around, so if you can push it in more in one place than elsewhere, then there's most likely an air gap.

Space at the back of the boot

Some space at the very back of the boot and even in the heel quarters is ok, if the toes are in all the way, and the boot shell hugs the hoof nicely at the front and sides. This kind of fitting issue sometimes happens with a horse with contracted heels. Flex pads can help in these cases, by filling out space at the back. You may also have space at the back of the boot if your horse has a round hoof that needs a wide style Flex Boot to fit the hoof width and length. Read more about our wide boots in this blog post.

If the horse is likely to overreach, and the boot is roomy at the back, then they can of course step on the boot and pull it off, just like a metal shoe that is too long behind the heels. Most of the time over-reaching is a trimming issue where the front feet don't leave the ground fast enough to get out of the way of the hind feet. Or the horse is moving beyond their natural and healthy range of motion. Some horses who clip the front feet with the hinds, will stop doing this as their balance improves and they no longer move on the forehand.

Gap at the top edge of the boot shell

If the boot shell is gaping at the top, first check that the boot has been put on straight and centered; a slightly off-centre application will cause the top to gape. Or on a horse with a crooked hoof (pigeon toed for example) and a little bit of flare, the gaping can happen quite easily. Once the flare is grown out, the situation will improve. Another reason why you might have gaping at the top is that the boot is simply too large. Ideally, for boot retention, you don’t want the boot to gape at the top.

Low hoof angles

Healthy feet with lower hoof angles are fine for Flex Boots. If a photo suggests that the hoof is too low in angle for the boots, the most likely explanation is that the whole hoof capsule has run forwards, both toes and heels, and if that's the case, the whole shell will look wrong and the TPU gaiter usually doesn't fit nicely either; there will be a gap between the TPU gaiter and heel bulbs, and the pastern strap doesn't close properly. The toes won't go in all the way and there will be lots of space from the middle of the toe walls upwards. These cases are very ill fits and primarily a hoof health issue (if the heels are crushed/too low, this is a significant problem for the horse) so we advise the customer to have the feet properly trimmed and for any inflammation to be taken care of for the horse’s sake. It's this kind of hoof with long toes and low angles that will break a Flex Boot sole in certain circumstances. Those horses are also at risk of injury: a long toe/low heel problem places great strain on the horses body, tendons and ligaments, but a small weekly trim to take the toes back will work wonders and creates positive changes in as little as a month.

My fit kit boot shell twists – is this a problem?

If the fitting shell twists, it doesn't necessarily mean that the actual boot will twist too. Once the straps are done up and pads added if necessary, most of these boots end up a nice snug fit. Again, if the toes go in well and there is space at the back, it's usually not a problem.

If the boots do tends to twist, adding a pad can make the boot a tighter fit and therefore reduce or eliminate twisting. But, in other cases, a larger size boot can help with twisting too; because boot twisting is caused by a problem higher up in the horse's body and/or how the horse moves its feet, each such case needs to be evaluated individually to identify the cause, so that the correct solution can be found.

My horse has deformed hooves or heel bulbs – will Flex Boots work for us?

Lots of horses with deformed hooves or heel bulbs are going well in Flex Boots. The boots are so soft that they tend to not irritate the injury. If the walls are misshapen, suitability depends on the severity and the individual fit. We’d say in most cases this would be ok. As long as the customer understands that if the fit ends up being a little bit off because of the hoof issues, and they can't be helped with trimming, the boot may not perform as flawlessly in terms of staying on if the horse does endurance riding for example. But we have fitted and sold Flex Boots to many horses with hoof issues like these, and all are happily being ridden without problems!


Do you want advice about whether Flex Boots would suit YOUR horse? Email us on and we will help you!

Just send us photos and measurements of your horse's feet, and we will get back to you as quickly as we can. Details of what information and photos we need from you can be found in this blog post.


Thanks for reading!

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