Correct me if I am wrong. As I know
B16B ori inlet size = 62mm, Butterfly size = 62mm, Outlet size = 62mm++
B16B inlet Bored size = 64.5mm, Butterfly size = 64.5mm, Outlet size = 65mm++
B18C-R ori inlet size = 62mm, Butterfly size = 62mm, outlet size = 67mm
B18C-R inlet Bored size = 64.5mm, Butterfly size = 64.5mm, Outlet size = 68~69mm
XXXX: My b16b TB butterfly size is 64.5mm.