Gilson Proceq HM-75L Original Schmidt Type L Concrete Test Hammer. Original Schmidt Type L Concrete Test Hammer is suitable for concrete testing in the same compressive strength range as the “standard” Type N model. However, the Type L model has lower impact energy to improve the repeatability of rebound values on cross-sections thinner than 4in (100mm). This minimizes surface blemishes and damage to brittle mixes.  The Type L test hammer is often preferred for testing precast concrete pipe sections and judging the strength suitability of cast-in-place concrete for form removal. Like Type N, Type L is a proven, efficient tool for the rapid assessment of concrete conditions, relative strength, and homogeneity. Accuracy can be further improved with correlation testing on compressive strength samples of identical mix designs. The HM-75L can be used in the ASTM test method D5873 for the determination of rock core strengths.