HT-20 Mortar Rebound Hammer Strength Measurement Range: 1.0-25 MPa Nominal Impact Kinetic Energy: 0.196 J (0.02 kgf·m) Impact Spring Extension Length: 75 ± 0.3 mm Static Friction Force of Pointer Slider: 0.5 ± 0.1 N Spherical Curvature Radius SR of Impact Rod: 25 mm Average Rebound Value Rm on Steel Anvil: 74 ± 2 Dimensions: 54 × 268 mm Weight: ≈1 kg Included accessories: HT-75 Brick Rebound Hammer Nominal impact kinetic energy: 0.735 J Impact spring extension length: 75 ± 0.3 mm Static friction force of pointer slider: 0.5 N ± 0.1 N Spherical curvature radius SR of impact rod: 25 mm ± 1 mm Calibrated rebound value on steel anvil: 74 ± 2 Dimensions: 54 x 268 mm Weight: ≈1 kg HT-225 Concrete Rebound Hammer Strength Measurement Range: 10-60 MPa Nominal Impact Kinetic Energy: 2.207 J (0.225 kgf·m) Impact Spring Extension Length: 75±0.3 mm Static Friction Force of Pointer Slider: 0.65 ± 0.15 N Spherical Curvature Radius SR of Impact Rod: 25 mm ± 1 mm Average Rebound Value Rm on Steel Anvil: 80 ± 2 Dimensions: 54 x 278 mm Weight: ≈1 kg