Three different solids of constant width 3cm. These are hollow and have internal stiffeners. Each is a solid of revolution from a different plane curve. You get a Reuleaux triangle, a rounded Reuleaux triangle, and a Reuleaux pentagon. All of them have width 3 cm in any direction. See this link
for these 3 models sold separately.
Check out other solids of constant width 3cm that work with these