Ravenox Heavy Duty Replacement Caps | Purple Martin Bird House QRC for Troyer Purple Martin Gourd Birdhouse Both Horizontal and Vertical (50 Pack) PURPLE MARTIN GOURDS REPLACEMENT CAPS: Purple Martin gourds offer a slightly different footprint from natural gourds. The deep cavity provides a real measure of safety from predators like owls, hawks and raccoons, in addition to a predator guard. Replacement caps are used to cover the access hole for the birdhouse and its subject to wear and tear outdoors. BIRD FEEDER AND REPLACEMENT CAP INSTALLATION: The bird guard replacement caps are UV protected with high-density polyethylene plastic unpainted caps. Some products require additional steps and materials, such as liners. Ravenox Purple Martin bird house replacement caps are ready to use when they arrive at your door. PURPLE MARTIN BIRD HOUSE FIT: Our heavy-duty bird feeder replacement caps measure 4 -inches in diameter and fit Ravenox Horizontal and Vertical gourds, SuperGourds, and Excluder Gourds. These caps will not fit natural gourd access ports. BIRD GUARD RIBBED CAP: Bird guard replacement caps are ribbed to provide a strong grip and easy removal. It fits the threaded access port. In turn, the port is used for gourd cleaning, nest cleaning and end of the season clean-outs. The replacement cap keeps these access ports securely sealed, protected and dry. GOURD BIRDHOUSE CAP RISK-FREE: We are a USA, CERTIFIED, Service-Disabled, Veteran-Owned, Woman-Led business that offers a one-year, money-back guarantee on all Purple Martin bird house and replacement cap purchases.