Butterfly Tenergy 05-FX has a Softer “Spring Sponge” that gives Better Control. TENERGY has proved an outstanding success combining High Tension Technology with “Spring Sponge”. TENERGY is well known; now there is a further development which maintains high performance levels with greater control. TENERGY 05 FX combines High Tension Technology with a version of “Spring Sponge” that produces a softer feeling. TENERGY 05 FX is the perfect answer for players who seek heavy topspin and superb control.