Small muffled flute (pinyin: xiǎo mèn dí), commonly known as leather whistle, is a double-reed gas-sounding instrument of the Yi nationality. In Yi language, it is called Yahalu or Benmaihei. In Yi language, "Benmaihei" means insect shell, and "Dili" means flute, which means the flute whose shell is used as a reed whistle.

The muffled flute is simple to make, easy to carry, has a mellow tone, and has strong expressive ability. It is popular in all parts of Chuxiong Yi Autonomous Prefecture in Yunnan Province and the Yi inhabited areas in Dali Bai Autonomous Prefecture, especially in Nanhua and Shuangbai areas in Chuxiong Prefecture and Nanjian Yi Autonomous County in Dali Prefecture. It is also spread in the Yi area of western Guizhou.

The muffled flute has a long history, but it is difficult to find out when and where it originated. According to many old folk artists in the Yi area of Yunnan, the ancestors of the Yi people used a small muffled flute to blow off the flood and saved the lives of the Yi family.

The traditional solo pieces for Xiaomendi include "Working Tunes", "Crossing the Mountain Tunes", "Asu Ze", "Shunning Tunes", "Sand Street Tunes", "Ma Cherry Blossoms" and so on.