These domes will fit all Resound/Siemens/Rexton/MA/Van/Ziv Sound, Thin and Flex tubes. These domes slide over the end of the tubes. Although the domes fit snugly on the Tubes they are easy to get on and off.
To get the size you need, measure the widest diameter of the dome in millimeters. These domes come five to a package (5) and are available in numerous diameter sizes.