Apparatuses for controlling gas flow are important components for delivering process gases for semiconductor fabrication. These apparatuses for controlling gas flow frequently rely on effectively sealed flow restrictors which can eliminate leakage of process gas around the flow restrictors. In one embodiment, a seal for a flow restrictor is disclosed, the seal comprising a plastic cylinder which is shrink fit onto a sealing portion of the flow restrictor. In another embodiment, a seal for a flow restrictor is disclosed, the seal having a first sealing ring with a flow aperture, a flow restrictor installed into the flow aperture.