The heavy (12 pounds) metal sleeve that moves up and down while pounding the sampling tube into the ground. Fits both the JMC Environmentalist's Sub-Soil Probe and the JMC Environmentalist's Sub-Soil Probe PLUS.
This extension lets you sample 3 feet deeper than the length of your sampling tube. (6 feet with a 3 foot tube) If you want to sample deeper than that you will need to purchase one or more JMC ESP Plus Regular Extensions in addition to this extension.