penetration type concrete strength tester leveraged strength method is used to measure nail penetration into concrete by nails, penetration depth and strength curve for conversion of concrete compressive strength of a new type of field test methods. this product conforms to the q/jy23-2001 standard requirement. technical parameters: penetration force:1000n±10n working stroke:20mm±0.1mm pin diameter measuring:3.5mm nail length measurement:40mm gauge groove:39.5mm