Improved 21 cm data on isolated galaxy pairs are presented which eliminate questions of inhomogeneity in the data on such pairs and reduce observational error to below 5 km/s. Quantization is sharpened, and the ‘zero’ peak is shown to be displaced from zero to a location near 24 km/s. An exclusion principle is suggested whereby identical redshifts are forbidden in limited volumes. The radio data and data from Schweizer (1987) are combined with the best optical data on close Karachentsev pairs to provide a cumulative sample of 84 of the best differentials now available. New 21 cm observations are used to test for the presence of small differentials in very wide pairs, and the deficiency near zero is found to continue to very wide spacings. A loss of wide pairs by selection bias cannot produce the observed zero deficiency. A new test using pairs selected from the Fisher-Tully catalog is used to demonstrate quantization properties of third components associated with possible pairs.