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.
This extension lets you sample three feet deeper provided you have a ESP Plus Sampling Tube and a JMC ESP Plus Master Extension. Regular extensions connect to each other for additional sampling depth capability.