This standard specifies the classification and code, size, shape, weight and allowable deviation of cold drawn or cold rolled precision seamless steel tubes, technical requirements, test methods, inspection rules, packaging, markings and quality certificates.
This standard applies …

One: water purifier and its purchase

Water purifier: a machine that purifies tap water

Precautions for purchasing a water purifier:

1, buy brand-name products

2, the purcha…