Abstract: A self-contained gas spring that has low heat generation characteristics and is easy to manufacture and maintain. The spring includes a bearing and seal assembly that is easy to remove from the cylinder body of the spring. The assembly includes an annular bearing for guiding the piston rod, the bearing is press fit within a bearing cap and, an end cap threaded in to the cylinder body. The end cap includes an annular seal surrounding and tightly engaging the piston rod of the gas spring. The end cap engages the bearing cap when the end cap is fully threaded into the cylinder body to retain the bearing cap within the cylinder body. The seal is formed of two materials, one very flexible, the other very rigid. The gas spring also has a unique piston head that has a hexagonal periphery with upwardly angled sides.