We have been wanting to make a mono-stirrup for a long time but have struggled with the dilemma of not being able to put them up for walking back and forth to the arena! We teamed up with Tether Shield in North Carolina to help us develop a system to get them up! All stirrup leathers come with the Tether Shield lock included.  
The leather is nylon reinforced with the buckle that hangs below the saddle flap to avoid scratching.  Excess leather tucks in nicely underneath.  Creates a slim, close contact and stable leather without the excess tail and buckle under the leg of a traditional stirrup leather. 
How to measure.  Measure your traditional stirrups in inches or centimeters from stirrup bar to where the stirrup starts.
Small- 17"-20" or 43cm - 50cm 
Medium-20"-24" or 50cm - 61cm
Large 24"-28" or 61cm - 71cm