Diffuse creatures can take a special -40% limitation on ST. If they take this limitation, they can only use their full ST on things of their own SM or larger. When they try to exert a force on something smaller than themselves, their ST is reduced in proportion to the difference in linear measurement for their SM. This is designed to simulate beings who are made of fluid such as air or water.
For example, consider a SM +10 whirlwind with ST 500. The Size and Speed/Range table tells us that SM +10 has a linear measurement of 100 meters. A SM 0 human has a linear measurment of 2 meters, so the whirlwind can only affect the human with 2/100 = 1/50 of its normal ST. It can push, lift, or batter the human as if it were ST 10.
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