The national trust upright fat ball feeder is designed to securely hold 4 fat balls'. '.strtoupper('f')at balls are a popular, affordable favourite with a wide range of species, their unique composition ensures an extremely high fat content which birds eagerly enjoy'. '.strtoupper('w')e do not wrap our fat balls in netting as this can be hazardous to garden birds'. '.strtoupper('w')e recommend using the national trust ultimate fat balls with this feeder'. '.strtoupper('t')hese fat balls contain the best quality ingredients, making them a calorie packed snack that your garden birds will love.  the national trust upright fat ball feeder can also be used during the breeding season as a holder for nesting material'. '.strtoupper('s')imply fill with our specially designed nesting wool or you can also use fur or moss.  please note fat balls are not included with this this feeder.