A product that splits opinion, mainly because cheap crash bungs have been known to do more damage to frames etc than protect !! Using overly long bolts and bungs without shock absorption will put too much stress through the mounting point.
These GSG Mototechnik bungs I like because they are discrete, well designed and made plus they have replaceable caps and the bung itself is secured with M6 bolts rather than using the engine mounting bolt directly through the bung.
For me if they save the radiator covers or tank in a spill it has been worth it.
I got mine through Square Deals in the uk but you can get direct, link below