Suitable for fitting into downspout pipes with an internal diameter of approximately 2.5" to 3", 3" to 4", 4" to 5", 6" to 7.5", 8" to 10", 9" to 11.5", 11" to 13". No unexpected tenants... The deliveries below are for mainland UK, for Highlands, Channel and offshore islands an extra charge per consignment will be applied as below, we can also arrange Saturday delivery at extra cost. Along with stopping birds from nesting in the chimney, wire balloons also prevent other issues. They stop birds from falling down the chimney and becoming lodged. There are reports of birds falling down chimneys when homeowners are on holiday. They then proceed to make a huge mess in the internal property over 2 weeks of unsupervised mayhem!