Solinst 110235 Well Cap Adapter, 4 Inch. The New Model 3001 Levelogger Well Cap Assembly is designed to fit 2", or 4" wells with a Reducer, and provides options for installing Leveloggers water level dataloggers with wireline, cord, or Direct Read Cables. The Well Cap can suspend a Levelogger and Barologger in one well, and still provides an access hole for other monitoring equipment. The Cap can be securely locked shut, and is vented to equalize atmospheric pressure.