If you have an ERT300, you can check your string tension and string bed stiffness using the Dynamic Tension (DT) value provided by the ERT300, along with the calculator below.

For Reference

Racquet Head Size

MID = (540 cm² – 610 cm²) or (83 sq inches – 94 sq inches)
MID PLUS = (611 cm² 680 cm²) or (95 sq inches – 105 sq inches)
OVER SIZE = (681 cm²  – 740 cm² ) or (106 sq inches – 115 sq inches)

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