I'm wondering how the syringe filters work and what size to buy. .45u or .20 u. I use 25g 1 1/2 inch pinz or 25g 1 inch pinz. But I draw with either an 18g 1 1/2 inch pin or a 20g 1 1/2 inch pin. Since I'm new to the whole filter thing any advise on how to use them would help too.