These are popular in Europe on certain winery and brewery equipment or systems. They do not interchange with Tri-Clamp or Acme threaded sanitary fittings. DIN 25 is 1" tube use suffix -100 (25mm), DIN 40 is 1.5" (40mm), DIN 50 is 2" (50mm), DIN 65 is 2.5" (65mm), DIN 80 is 3" (80mm), DIN 100 is 4" (100mm).