Check the listing for details. Seachem Filter Sock Small 250 Micron Mesh Fine Polyester with Plastic Collar. Condition: New. Listed at 12.99 USD. Seachem Filter Sock Small 250 Micron Mesh Exceptional particulate removal for superior water quality.Overview:Filter socks are a critical component in maintaining water quality in aquariums. They remove suspended debris and detritus, which often lead to excess dissolved organics, nitrate, and phosphate when left unchecked. This makes Seachem Filter Socks an integral addition to any sump and overflow system.Seachem Filter Socks feature durable, welded seams and have a singed finish, which reduces wear and prevents release of fibers back into the water column.In addition to the choice of a 100 micron felt, 200 micron felt and 250 micron fine mesh rating for exceptional particulate removal, they feature welded seams, which, unlike threaded seams of similar products, will not breakdown over time. They have a singed finish, which reduces wear and prevents release of fibers back into the water column. Finally, the plastic collar simplifies installation and easily fits standard sump fittings. Size: 250 Micron Fine Mesh - Small 10 x 30 cm / 4” x 12” (10 cm / 4” plastic collar)