A seal, comprising: a bellows spring including a plurality of walls that define a chamber having a volume containing a pressurized gas, said bellows spring comprising a mechanical spring and said pressurized gas comprising a gas spring, wherein a sealing force generated by the seal at a target operating condition is decoupled from the physical properties of the mechanical spring; wherein: said bellows spring includes an outer side, said outer side having at least two outer walls (72, 74) and said bellows spring having an inner side, said inner side having at least two inner walls (76, 78), said outer walls (72, 74) attached one to the other to form said outer side and said inner walls (76, 78) attached one to the other to form said inner side and said outer side attached to said inner side to form said bellows spring having said chamber, said chamber being filled with a pressurized gas; and an upper outer wall is attached to an upper inner wall at a first weld joint and said upper inner wall is attached to a lower inner wall at a third weld joint and said lower inner wall is attached to a lower outer wall at a second weld joint and said lower outer wall is attached to said upper outer wall at a fourth weld joint to form said bellows spring; characterized in that at least one of said walls (72, 74, 76, 78) has a contoured cross-section. a bellows spring including a plurality of walls that define a chamber having a volume containing a pressurized gas, said bellows spring comprising a mechanical spring and said pressurized gas comprising a gas spring, wherein a sealing force generated by the seal at a target operating condition is decoupled from the physical properties of the mechanical spring; wherein: said bellows spring includes an outer side, said outer side having at least two outer walls (72, 74) and said bellows spring having an inner side, said inner side having at least two inner walls (76, 78), said outer walls (72, 74) attached one to the other to form said outer side and said inner walls (76, 78) attached one to the other to form said inner side and said outer side attached to said inner side to form said bellows spring having said chamber, said chamber being filled with a pressurized gas; and an upper outer wall is attached to an upper inner wall at a first weld joint and said upper inner wall is attached to a lower inner wall at a third weld joint and said lower inner wall is attached to a lower outer wall at a second weld joint and said lower outer wall is attached to said upper outer wall at a fourth weld joint to form said bellows spring; characterized in that at least one of said walls (72, 74, 76, 78) has a contoured cross-section. said bellows spring includes an outer side, said outer side having at least two outer walls (72, 74) and said bellows spring having an inner side, said inner side having at least two inner walls (76, 78), said outer walls (72, 74) attached one to the other to form said outer side and said inner walls (76, 78) attached one to the other to form said inner side and said outer side attached to said inner side to form said bellows spring having said chamber, said chamber being filled with a pressurized gas; and an upper outer wall is attached to an upper inner wall at a first weld joint and said upper inner wall is attached to a lower inner wall at a third weld joint and said lower inner wall is attached to a lower outer wall at a second weld joint and said lower outer wall is attached to said upper outer wall at a fourth weld joint to form said bellows spring; characterized in that at least one of said walls (72, 74, 76, 78) has a contoured cross-section.