Abstract: An orifice plate holder for removeable insertion between juxtaposed flanges, the holder being formed of a plate body portion of rigid material having an opening therethrough, first and second elastomeric washer members having an outer diameter greater than the plate body portion opening and sealed to the opposed sides of the plate body portion, one of the washers being sealed only approximately one-half of its circumference so that the unsealed portion is resiliently deflectable away from the body portion, and an orifice plate insert of rigid material and of outer diameter less than that of the opening through the plate body portion, the orifice plate insert being insertable between the elastomeric washer members so that the assembly may be removeably positioned between adjacent flanges and tightened in position, the orifice plate insert being thereby easily replaceable as it wears or when it is desired to change to a different size orifice.