Round mandrel slip joint is specifically designed for floating vessel operations (such as formation testing\hook wall testing \acidizing & fracturing, etc.). Its purpose is to provide an expansion joint in the string to help compensate the up and down movement of floating drilling vessel. It can compensate the contraction and expansion caused by the temperature and pressure change on land test. This telescoping tool can also be used below the muti-flow test valve to provide a free travel when manipulating the pipe to reposition the tester valve during a test.