The roundness of the reducing elbow should not exceed 1% of the corresponding outer diameter of the end, with an allowable deviation of ±3mm. The material for the reducing elbow complies with SY/T5037, GB/T9711, GB/T8163, ASTM A106/A53 GRB, API 5L, APT5CT, ASTM A105, ASTM A234, ASTM A106, DIN German standards, and customer-specified standards. Reducing elbows (also known as reducers) are pipe fittings used at pipe diameter changes. Common forming processes include reduction pressing, expansion pressing, or a combination of both, with stamping forming also applicable for certain sizes.