BK-G4 are compact commercial diaphragm gas meters designed to meet the highest demand with respect to accuracy,reliability and safety.They incorporate both innovative features and Elster's gas measurement know-how of many decades.The strok of the diaphragms is preumatically stopped. This ensures low bearing loads and quiet operation.The proven and patented K-system and the use of high-grade material ensure a high quality standard and a long service life.Due to the small slides,they are stable in registration at Qmin.and the meter is not susceptible to contamination or change of friction (RPF to BS4161). Error curve of measuring units are adjusted by K-system.Robust design.