What camera strap connection type should I choose?

Flat Mount

Canon style flat or slotted lug mount camera strap attachment

Best for: most Canon; entry- and mid-level Nikon; Fujifilm GFX (connect strap to Fuji-supplied attachment clips), X-T100, X-A Series; vintage Rolleiflex. Also known as a “slotted” or “rectangular” mount.

Lug Mount

Nikon style lug mount camera strap attachment

Best for: pro-level Nikon; Leica; Olympus; Sony; most Fujifilm; most vintage 35mm cameras. Also known as a “round” or “ring” mount.