inserted in a u201c flaccid u201d state into the center bore 130 and the magnetic induction apparatus 100 is activated to allow the penile prosthesis to assume a u201c rigid u201d state and thus create a simulated erection such as shown in fig1 the sheath may be compliant with the expanding geometry of the shape memory alloy penile prosthesis allowing eddy currents to run in a close loop perpendicular to the variable magnetic field the sheath 110 may take different shapes such as having varying cross sections or thicknesses as long as the penis with the penile prosthesis is able to fit within the bore 130 without contacting the sheath 110 the length of the sheath 110 may range from about 15 cm to about 30 cm long from about 15 cm to about 20 cm from about 20 cm to about 25 cm and from about 25 cm to about 30 cm the sheath 110 may have a bore 130 for the insertion of the penis with the penile prosthesis of at least about 4 cm diameter in various embodiments the sheath 110 may be available in a variety of lengths and bore diameters to provide for a user to have a magnetic induction apparatus 100 of an appropriate size in various embodiments the magnetic induction apparatus 100 may be rigid flexible or have a combination of rigid and flexible components in an embodiment the magnetic induction apparatus 100 may be a wearable device in other embodiments the magnetic induction apparatus 100 may be linear or shaped like a u201c wand u201d the wand may be hand held and moved over the penis shaft in a back and.