If they are like mine, they look like Lewmars, but are actually made by Bowmar. I have not found any way to disassemble them to replace the gasket. However, I have found that if the gasket is not torn, you can clean and lubricate it with silicone grease (wiping off any excess) and the dripping will stop. This seems to recondition and soften the rubber. When the gaskets finally give out, I'm afraid that replacement of the whole port will be necessary.