This 3mm diameter Neoprene sponge cord can be used under the bezel rings of chronometric and magnetic speedo/rev clocks of all sizes, in a similar manner to the O ring (Item number Speedo_06). It is supplied in a 20" length that can be cut to size, but this length should be sufficient to complete two 80mm (standard chronometric size) instruments. The sponge cord material is slightly softer than the O ring material