Nectar Guard tipseasily slide onto the feeding ports on the underside of the Aspects Hummingbird Ultra feeder cover and HummZinger Fancy Hummingbird feeders (Feeders Not Included) The flexible membrane in the center of each tip easily opens when hummingbirds insert their beaks to feed and close up tight when beaks are removed. Nectar Guard tips create a barrier flying insects can't penetrate. Package of 12 tips. Prevents wasps and bees from contaminating nectar. Each tip is about 1/3 inch long. For use with HummZinger Ultra and Fancy hummingbird feeders.