A protective boot formed of a resilient elastomeric material is provided having a housing with an opening therein through which the reciprocating shaft of a solenoid or like device projects with the shaft being axially movable relative to the housing of the solenoid through a stroke of a predetermined length from an extended position to a retracted position. The protective boot includes a first ring portion sealingly fixed to the housing about the opening and, a second ring portion sealingly fixed to and reciprocatable with the shaft. The body portion of the boot forms a fluid chamber about the shaft between the first and second ring portions, with the body portion comprising at least one pair of truncated conical sections each being integrally formed at their narrow portion with a respective one of the ring portions and an intermediate portion integrally formed between the widened portions of the conical sections. The conical sections and the intermediate sections are provided with axial convolutions, ribs, or both for maintaining the conical sections and the intermediate portion axially rigid during movement of the shaft between the extended position and the retracted position. These convolutions or ribs also permit the conical sections and the intermediate portion to circumferentially expand and retract during movement of the shaft between its extended position and its retracted position to maintain an essentially constant volume within the fluid chamber.