Reference for Kelim 24:11

שָׁלֹשׁ חֲמָתוֹת וְשָׁלֹשׁ תּוּרְמְלִין הֵן. הַמְקַבְּלִים כַּשִּׁעוּר, טְמֵאִין מִדְרָס. וְשֶׁאֵינָן מְקַבְּלִין כַּשִּׁעוּר, טְמֵאִים טְמֵא מֵת. וְשֶׁל עוֹר הַדָּג, טָהוֹר מִכְּלוּם:

There are three types of water skins and three types of pouches: those which can hold the prescribed measure are susceptible to <i>midras</i> uncleanness; those which cannot hold the prescribed measure are susceptible to corpse impurity; and that which is made of fish hide is pure from all [types of impurities].

Jastrow