The guide says I should use a 17, got one and it was too tall, did a return/swap and got a 13, it was perfect. Put a taller seat and helibars so ordered a 15 and now have both. At 6'2 I look over it a good bit but the air flow it still well over my head, even the 13 still works good. I can still duck down behind it if I have to run in the rain without my full face. Being able to replace or add another size is low cost after you have the base shield. Plus with the base dark and the taller clear it still looks good and really tall shields don't in my opinion. After many miles it is holding up well, no scratches or discoloring.