The EN ISO 3452-3 Type 1 Reference Block for testing sensitivity of fluorescent and visible penetrant systems consists of 4 nickel-chrome plated panels with 10, 20, 30 and 50 µm thickness of plating respectively. The panels have crack depths of 10, 20 and 30 µm. The sensitivity of visible (contrast) penetrant systems is determined by using the 30 and 50 µm plated panels. These panels are rectangular in shape with typical dimensions of 35×100×2 mm. Transverse cracks are made in each panel by stretching the panels in the longitudinal direction. The width to depth ratio of each crack should be approximately 1 : 20. A declaration stating conformance to EN ISO 3452-3 and in line with EN 10204, Type 3.1 B shall accompany each test block.