When components with stiffnesses $K_1$ and $K_2$ are considered to be in series, the effective stiffness $K_e$ is given by $\frac{1}{K_e} = \frac{1}{K_1} + \frac{1}{K_2}$. If $K_1 = K_2$, then $K_e = 0.5 K_1$.