Abstract: An inertia bar to be installed in a well between a sucker rod string and a subsurface pump. A string of the bars adds weight to the sucker rod string and maintains it under tension throughout a pumping cycle. A sufficient number of the bars are used to place a neutral zone within the inertia bars. The neutral zone is a zone in which there is neither tension nor compression in the bars. The body of each bar has a relatively large diameter, which for example may be the same as the outside diameter of the couplings used to connect the individual sucker rods. The bar has pins at its ends for engaging the couplings, which pins have the same dimension as standard sucker rod pins. The bar can be engaged by a conventional elevator when it is to be removed from a well.