Warning: Falls from horses involve high levels of energy so wearing a body protector cannot guarantee to prevent injuries but should ensure that any injuries are  reduced in severity. Body protectors do not prevent injuries involving severe torsion, flexion, and extension or crushing and do not protect against spinal injuries.
It is very important that your body protector not only fits correctly around your body, but is also the correct length, as, if it is too short it will not provide the correct protection and if it is too long it will ride up off your shoulders. This is, in fact, uncomfortable and in a severe case it may cause you to become unbalanced and possibly fall off your horse. The diagram shows the positions for the measurement of the control dimensions A,B,C and D stated by the manufacturer and used in sizing the protective clothing.
To function correctly body protectors should be a snug fit; as garments which are too large can be displaced in an accident. Take measurements , as per the diagram, while wearing normal underclothing or snug fitting thin outer clothing and select the appropriate size from the chart.