PBC Linear NIM20SS 0300 SL Linear Shaft, Solid Shaft, 20 mm Dia, 300 mm Lg, Stainless Steel 31A846 They have a built in check They have a built in check valve that reduces spillage when withdrawing the nozzle from tank make sure your screw has a comparable strength rating Linear Shaft Lined Bearings Surface Roughness 8 12 RMS Product Type Linear Shaft Standards ISO Shaft Drilling Undrilled Shaft Material Finish Polished System of Measurement Metric Shaft Material Grade 440 Shaft Material Stainless Steel End Type Plain Ends Series NIMSS Roughness 8 12 uin RMS Shaft Type Solid Shaft Tolerance Class M Core Type Solid Surface Hardness Minimum 50 HRC Weight Per Meter 2