I bought these shrouds after hearing that they would slim up the front of the bike. They took about a centimeter off of the width of the bike but the shape is a bit different around the top of shroud which makes it feel slimmer. I haven't seen any difference or cooling but the woosh sound from the airbox on my 2012 yz450f has definitely quieted down a bit. Fitment was tight but they did go on. Graphics went on easily and did need to be trimmed to get a clean look.
I gave this product an average score for this application: 2010 YZ450F
Installation was problematic, there seems to be substantial bending required to make item fit.
Overall, the build quality of the product is very good, but I'm not sure they improve over the stock radiator shrouds.
Once installed they look very good and perform as advertised.
NOTE: if a graphics kit is intended for installation with this item, remember most if not all graphic kits are designed for STOCK radiator shrouds. Graphic kits will fit, but trimming is required and fit is not perfect.
These things look good on the bike, and fit perfectly, but they are tough on shroud graphics. Installation of stickers is difficult due to the complex curves and a shape that is slightly different from OEM. Can't really tell if they effect cooling.