Dialysis filters, also called dialyzers, are the core components of hemodialysis machines that remove waste products (urea, creatinine), excess fluids, and electrolytes from blood via diffusion and ultrafiltration across semipermeable membranes. Hollow fiber dialyzers (most common) contain 8,000-15,000 microporous capillaries (200µm internal diameter) made from synthetics like polysulfone/PSu (high-flux, excellent biocompatibility) or cellulosics (low-flux, economical); plate-and-frame and coil dialyzers offer alternatives for specific clearances. Blood line filters (tubular/mesh, 40-300µm) trap clots/microemboli; dialysate filters (0.2µm) ensure ultrapure water. Surface area (1.0-2.2 m²), Kuf (ultrafiltration coefficient), and β2-microglobulin clearance determine performance.