XLS-A Filter Patch Bags, .5 Micron 10-15 lb sawdust Bulk SubstrateXLS-A filter patch bags. 10″X5″X24″ 3.0mil thickness PP Filter 2″X3″ 0.5 microns. These are great for 10-15 lb sawdust blocks. Our go to bag for sawdust block production. These are empty unicorn  bags that you can make your own substrate blocks with. They can be put in a pressure cooker/ steam sterilizer to sterilize the substrate of your choice. Fill these bags with the substrate of your choice and innocualte with whatever culture you want. ( note this is for the more adventurous/experienced mushroom cultivator ) Alternativley you can use these bags for the hydrated lime pasteruization method of substrate as well although I can offer other long  poly tube bags without the filter patch in long sections if you want to try making large substrate bag. Check the other poly tube bags for this( will be great for straw mushroom blocks ) $30 for 10 or $100 for 50