The Ultrabag was launched a couple of years ago as there was a need to clarify stocks quickly with no mess or fuss. Prior to this, Chef’s used filter papers or Muslin and neither had a great result. The Ultrabag comes in various sizes and in either 100, or 200 microns ( measurement of holes ). Using this bag you can accomplish perfect clarification in one pass, that takes seconds, then empty and wash, then reuse. Simple effective and inexpensive. John Lethlean recently wrote this article on how it is used. Please have a read.