Goldfinches will feed upside-down but House Finches won't. Small sized holes dispense Nyjer economically. Birds must pull seed out. Cap and base are made of sturdy ABS, UV stabilized plastic. The sloped base keeps seed within easy reach of the birds. The UV stabilized polycarbonate seed tube won't degrade in the sunlight. Caps lift off easily to allow re-filling and thorough cleaning and the design of the cap makes it difficult for predators to lift and reach the seed. Your feeders can be hung or pole mounted using Droll Yankees Ultimate Pole System. Optional seed trays attach easily to catch spilled food and also provide extra perching space. Cleaning.. Please, for the sake of the birds keep your feeders clean! Wash regularly in a 50/50 solution of hot water and white vinegar, rinse thoroughly and refill when completely dry. Dirty feeders spread disease.