best bit of kit i ever bought derby house do them for £10
heres some info i found on them
Mane and tail thinners are an ideal way of finishing, shaping and thinning your horses mane and tail.
A bushy, unkempt tail can be transformed to a tidy pulled tail with no discomfort to the horse.
Mane and tail thinners give a well-tailored and professional finish in minutes.
They can even be used on anxious horses.
Mane and tail rakes are ideal for touching up forelocks or thinning manes leaving a natural pulled finish.
I love mine! I've never pulled a tail before, & decided to go for it cos it looks more prof than plaiting & saves a fiddly job on show mornings.
I would say that if you get one, have a play with it but do less than you want to, then revisit every couple of days so you don't go mad & end up with a bald horse!
I got one from clippersharp with a wooden handle, you can get the blades sharpened and different blades for fine or coarse hair. I use mine to thin manes and give tails the pulled look without actually pulling. A very useful piece of kit!