The ability to change stiffness is a capability exhibited through the animal kingdom, with many recent advances in tunable stiffness in the area of robotics. In this paper, we propose a mechanism design that provides the ability to make modular subcomponents with tunable stiffness by creating a bi-stable mechanism that exhibits different stiffnesses in each of the stable configurations. The design is based on controlled buckling of two linear springs in series and allows design-time control over the stiffnesses, equilibrium points, and energy required to transition between the stable configurations.