Tillett CIK FIA P1 Defender Rib Protector, Black, Size XS

Size guide : 
The P1 Defender is available in sizes relating to height and chest circumference.
Each hight window has a number of circumference choices. 
To wear it as intended by FIA regulation, your height must fit in the correct height window, or one height category shorter. 
To find your correct chest circumference use a measuring tape pulled tight around the chest. The measurement position shown on the diagram as a red line, is around nipple height for man and young children. the driver should breathe in and out, taking note of the average circumference. It is strongly advised to choose a rib protector that is not too large. When sizing a rib protector, the fit should be viewed exactly as you would fit a crash helmet, with no gaps and definitely not loose. If the driver is between size choose the smaller size and always use the additional 30 mm adjustment at the rear before choosing the next size up.

With the CIK Karting body protector, the correct height of side panel is regulated. The height of the user is measured from the bottom of the feet to the top of the head with the subject standing upright and wearing neither shoes or helmet. 
You must choose a protector that matches your height, if the circumference required falls outside of your height range, or one height size down, a special may be required to keep the protector fit within in the regulations. 

Find information about the Adjustment here
Find information about the correct fitting here