A hermetic seal, primarily for compressors (12) for use in refrigeration of air conditioning systems but having use in apparatus wherein a seal is required between two elements (14, 14) reciprocating substantial distances relative to each other, comprising a bellows having a plurality of convolutions (17, 19, 21) with positive displacement means (25, 26; 27, 28) associated therewith that assures simultaneous movement of most of the convolutions upon rapid acceleration of relative movement between the two elements. This prevents excessive stress and strain on any one or more convolutions or on the end convolutions in particular, as to cause failure thereof, by distributing the stress over a large number of the convolutions rather than just a few at any one instant. The stress in each convolution of the bellows depends upon the natural frequency and spring rates of any given bellows diameter and number of convolutions. Also, the stresses in the various convolutions depend upon the location of and the number of divisions that have positive displacement means for actuation thereof, (engine) speed and piston acceleration. By proper selection of the number of convolutions in each division, which may vary in numbers, it is possible to make a bellows of substantial length wherein the stress level in each bellows convolution will be substantially equal.