You may be referring to a tire.
balloon
One of the spaces in different parts of the bodies of birds, which are filled with air and connected with the air passages of the lungs; an air cell.
no there made of leather on the outside but with some rubber in the inside then just filled with air.
an air filled sac near the spinal column in many fishes that helps maintain buoyancy.
A fluid-filled sac that surrounds an embryo is called an amniotic sac. This sac contains amniotic fluid, which provides protection and cushioning for the developing embryo.
Professional soccer balls are typically filled with a combination of air and latex or butyl rubber bladders.
Amniotic sac
the air sac itself.
The fluid-filled sac surrounding the developing embryo or fetus is called the amniotic sac. It is filled with amniotic fluid that protects and cushions the fetus, helping to regulate its temperature and provide room for movement.
If a membrane-bound sac filled with large molecules of oil is suspended in a beaker of water, water will start to enter the sac. The sac will then swell.
The stomach
A closed sac with fluid in it