The MTEK FLUX's helmet shell is the same size no matter what helmet size you have (the only difference between the two sizes if the internal helmet padding) so no matter what helmet cover you select you will be getting the same size cover and it will fit your MTEK FLUX perfectly.
For the Hard Head Veteran helmet, we recommend going with the helmet bridge. It is universal so it will be sure to fit your helmet. You can check it out here: https://agilitegear.com/products/bridge-tactical-helmet-accessory-platform .
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