This inner-ring for ASFA, worm-drive clip with 9mm and 12mm bandwidth, was designed to give extra protection to the hose, especially where it enters into contact with the underside of the clamp housing.
Inner-rings are particularly recommended for use with silicone hoses which are quite fragile and can be cut easily. The inner-ring ensures a good fit, prevents damage to the hose and also contributes to an even distribution of pressure around the hose.
The black coating helps to ensure that the rings adapt correctly to the hose assembly
