Apparatus and methods are disclosed which seek to reduce stress formation in potting heads for porous hollow membranes. A potting sleeve (5) is disclosed for use in forming a potting head having a porous hollow membrane mounted therein wherein the potting sleeve (5) includes at least a portion (17) thereof movable to reduce the peripheral extent thereof. A method of mounting a porous hollow membrane in a support structure of a membrane filtration apparatus is disclosed comprising: providing a mould for receiving potting material (51); positioning one or more deformable members (50) within the mould; positioning a portion of the porous hollow membrane to be mounted within the mould; and introducing a curable potting material (51) into the mould so as to immerse the portion of the porous hollow membrane and at least part of the one or more deformable members (50) in the potting material; at least partially curing said potting material (51) to form the potting head and removing the potting head (52) and the one or more deformable members (50) from the mould. "4m ,,/z /<
