Non-standard flanges do not follow any national standards. Those with standards are not non-standard flanges; they are standard products. Non-standard flanges, or those with different sizes or bolt hole centers, are not round like conventional flanges but may be triangular. All non-standard flanges require custom manufacturing. It's not realistic to have a factory produce a non-standard flange and wait for customers to come. If such products are produced in bulk, they are no longer considered non-standard; they are standard products. For instance, if a batch of 10,000 non-standard flanges is produced, they are then considered standard, at least in the producer's eyes. The fewer the quantity, the higher the price, which is an industry consensus. Producing a few non-standard flanges requires labor and materials, which is predictable. A slightly higher price is understandable. All customers seeking customization must provide drawings or technical specifications. Without these, production is not possible. Some non-standard flange models are close in normal specifications, such as chamfering and surface finish, similar to standard models unless specified otherwise. The term "non-standard flange" for this product essentially means the same thing; there is no real difference in meaning when looking at it purely from a literal standpoint. Such products all require custom manufacturing.