The PARVEEN Mechanical Spring Jar is designed to deliver a very high upward impact load during wireline operations. It is especially useful when working in high pressure gas wells where hydraulic jars are susceptible to seal failure. The spring jar can be adjusted for a predetermined release force, therefore offering the operator a desired force at the tool. The load setting is done with a calibrated box spanner supplied with the spring jar. A hydraulic load calibration sub is available as an optional extra to allow the operator to set and test the load rating of this spring jar.