The PU Letter

[Randy W]

PU letter for M visa, if you have urgency to deal in China. this is the only way to apply Visa.

A PU letter is an official letter of invitation for business and work purposes issued by the provincial Foreign Affairs Offices (FAO) in China. The FAOs in different cities have various requirements and processing times. “PU” stands for “普通” in Chinese, which means the letter is issued to ordinary passport holders.

By Google Translate, 普通 Pǔtōng means ordinary, common, or general.
The letter says 邀请函 or Yāoqǐng hán, which means Invitation letter.

from Going to China on Facebook (post no longer exists)
https://www.facebook.com/groups/going2china/permalink/4097495190378821/

from Chengdu-Expat
The Ultimate Guide to the PU Invitation Letter