The Daiwa Shallow Spacer Unit 20mm is designed to increase the usable depth of any compatible tray, making it easier to store deeper winders and bulkier accessories. Its construction includes a ridge and recess compression seal for a secure, watertight fit, along with a perforated base for effective drainage and airflow. - Shallow spacer unit features a ridge/recess compression seal and perforated base - 20mm depth lets you extend any tray depth for deeper winders and accessories