Methyl Cyanoacrylate, for metal bonding, and Ethyl Cyanoacrylate, for plastic and rubber bonding, are used principally in industrial applications. Octyl Cyanoacrylates and Butyl Cyanoacrylates are used principally in Medical Applications. Butyl esters provide stronger bond, but are rigid. Octyl ester, while providing weaker bond, are more flexible. Medical Adhesives need to be cause less sensitivity issues to skin.