This paper presents a selective magnetic resonant wireless power transfer (WPT) system, consisting of a transmitter (TX), a tunable intermediate-resonator, and a receiver (RX). In the proposed WPT system, the tunable intermediate-resonator can be either a relay resonator or an intermediate-RX by varying its variable resistance, demonstrating the flexibility of the intermediate resonator to be used for different topologies and applications. This flexibility will enable the proposed WPT system to transfer maximum energy efficiency to various distances between the TX and the RX, to longer distances for the WPT relay system and to shorter distances for the intermediate-RX system. In this case, the WPT intermediate-RX system has a larger power transfer efficiency than the WPT relay system.