The ovality of the reducers should not exceed 1% of the corresponding outer diameter of the ends, with an allowable deviation of ±3mm. The materials for the reducers comply 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 for reducers (elbows). Reducers are pipe fittings used at locations where the pipe changes diameter. Common forming processes include diameter reduction and pressing, diameter expansion and pressing, or a combination of both. For certain sizes, stamping forming can also be applied.