The round mandrel slip joint is designed and manufactured according to NACE MR0175, and suitable for working in H2S abouve 175oC and full H2S working condition.The round mandrel slip joint likes other slip joints, accepts the movement associated with ocean heave or temperature change without allowing the movement to disturb the placement of downhole tools. The slip joint can also accommodate any changes in string length caused by temperature and pressure during a downhole test. The round mandrel slip joint is composed of two distinct parts: an outer housing and a moving inner mandrel.