to find the correct size.use a tape measure around your head approximately 2 cm.above eyebrows and ears and take a note of the measurement in centimetres.once you have decided on your ideal heomet according to your measurements,try i on and ensure that it fits correctly.you should feel a positive pressure around your head without any tight spots.if the helmet fits too loosely it may bi rolled off your head in the event of an accident.as you wear the helmet more and more it will adapt slightly to the shape of your head.secure the helmet fastening and check it works safely by pulling the helmet up making sure that it does not come off.if possible,leave the helmet on for a few minutes to check there are no pressure points or tight spots