This Aluminum Sump - 50pc 16mm ID 20mm OD Washer is perfect for small home projects or industrial applications. Made of durable aluminum, these washers are corrosion resistant for long-term use. With an inner diameter of 16mm and an outer diameter of 20mm, these washers are designed to provide a secure, reliable fit. When you need flexibility and strength, this sump washer is the best choice.