Dual Horizontal Round Rail Mount 78 or 1 Summer Savings Sale! Save 20% or More on Magma! Price Shown Reflects Discount. Horizontal Rail Mount Fits Standard Round Rails 78 or 1 22mm or 25.5mmThese incredibly strong rail mounts have a unique pivoting design which allows them to mount to straight or curved rail or across the corner of a stern rail. Made of 18 8 stainless steel and 356 anodized aluminum, they instantly detach without tools for compact storage.