A hydraulic cylinder comprising: a cylindrical tube having a tube inner surface, a tube outer surface, a tube first end, a tube second end opposite the tube first end, and a first fluid port proximate the tube first end; a piston head disposed within the cylindrical tube; a piston rod connected to the piston head and extending outward from the cylindrical tube through the tube second end; a cylinder head having a piston rod opening receiving the piston rod and having the piston rod slidable therethrough, wherein the cylinder head is inserted into and engaged by the tube second end of the cylindrical tube to retain the cylinder head therein; and a cylinder cap having a cap sealing portion with a cylindrical shape and a cylinder attachment portion, wherein the cap sealing portion has a plurality of annular cap grooves (142, 142A, 142B) defined in a sealing portion outer surface, wherein the cap sealing portion is inserted into the tube first end and the tube outer surface proximate the tube first end is crimped down onto the cap sealing portion so that a tube material of the cylindrical tube at the tube inner surface proximate the tube first end is disposed in the plurality of annular cap grooves (142, 142A, 142B) to retain the cap sealing portion within the tube first end and seal the tube first end of the cylindrical tube, wherein the plurality of annular cap grooves (142, 142A) has a rectangular cross-section, or wherein a cap groove width of each of the plurality of annular cap grooves increases as the plurality of annular cap grooves extends inward from the sealing portion outer surface. a cylindrical tube having a tube inner surface, a tube outer surface, a tube first end, a tube second end opposite the tube first end, and a first fluid port proximate the tube first end; a piston head disposed within the cylindrical tube; a piston rod connected to the piston head and extending outward from the cylindrical tube through the tube second end; a cylinder head having a piston rod opening receiving the piston rod and having the piston rod slidable therethrough, wherein the cylinder head is inserted into and engaged by the tube second end of the cylindrical tube to retain the cylinder head therein; and a cylinder cap having a cap sealing portion with a cylindrical shape and a cylinder attachment portion, wherein the cap sealing portion has a plurality of annular cap grooves (142, 142A, 142B) defined in a sealing portion outer surface, wherein the cap sealing portion is inserted into the tube first end and the tube outer surface proximate the tube first end is crimped down onto the cap sealing portion so that a tube material of the cylindrical tube at the tube inner surface proximate the tube first end is disposed in the plurality of annular cap grooves (142, 142A, 142B) to retain the cap sealing portion within the tube first end and seal the tube first end of the cylindrical tube, wherein the plurality of annular cap grooves (142, 142A) has a rectangular cross-section, or wherein a cap groove width of each of the plurality of annular cap grooves increases as the plurality of annular cap grooves extends inward from the sealing portion outer surface.