Abstract: A downhole centralizer arranged to receive a downhole tubular has a tubular body with opposed ends and is formed of plastics material A respective end ring is mounted in the or each opposed end and is formed of a plastics material having a Youngs Moldulus no greater than that of the tubular body.

Abstract: A removal impact cover (14) for a marine riser buoyancy module (10) has an arcuate shape with an open face (21). The cover (14) has a number of recesses (18) arranged to engage with recesses (22) on the module (10). The recesses (18) each contain an aperture (20) and the recesses (22) each contain an aperture (23). The cover (14) and the module (10) are engaged by fastening means preferably extending the apertures 20 and 23. More preferably the engaged cover (14) is spaced from the module (10) to reduce direct transmission of forces to the module (10).