Abstract: A valve for a displacement pump includes a valve body having an annular strikeface and defining an annular receptacle, and an annular seal received in the receptacle of the valve body, the seal including an annular contact surface, wherein the seal defines a cumulative displacement ratio of (i) at least one of at most 0.20 at a location that is spaced 40% from an inner diameter (ID) of the contact surface of the seal moving towards an outer diameter (OD) of the contact surface, (ii) at most 0.35 at a location that is spaced 55% from the ID of the contact surface moving towards the OD of the contact surface, and (iii) at most 0.45 at a location that is spaced 65% from the ID of the contact surface moving towards the OD of the contact surface.

Abstract: A body adapter for a stringed musical instrument, comprising: a bottom portion and a varying thickness perimeter sidewall portion, where a space bounded by the bottom portion and an inside portion of the perimeter sidewall portion, forms a receiving compartment. The receiving compartment has a shape adapted to releasably receive the body of a stringed musical instrument and thereby change the shape of the instrument as it is held by a user for playing, from that of the outside shape of the musical instrument, to the outside shape of the body adapter.

Abstract: A body adapter for a stringed musical instrument, comprising: a bottom portion and a varying thickness perimeter sidewall portion, where a space bounded by the bottom portion and an inside portion of the perimeter sidewall portion, forms a receiving compartment. The receiving compartment has a shape adapted to releasably receive the body of a stringed musical instrument and thereby change the shape of the instrument as it is held by a user for playing, from that of the outside shape of the musical instrument, to the outside shape of the body adapter.

Abstract: A piston head assembly for reciprocating in a cylinder is disclosed, the cylinder having an inside surface and the inside surface having an inside diameter, comprising: a piston head including a central portion and a flange, the flange having a diameter that is no more than 0.010 inches less than the inside diameter and an annular seal removably mounted on the flange, the seal including a lip and a heel, the lip having an uncompressed diameter that is at least 0.20 inches larger than the inside diameter and the heel being free of a separate retaining means. The seal can also be manufactured so as to be free of any annular depression in its outer surface.