What is the formula to make a concentric reducer?

A concentric reducer is typically designed using the formula for the volume of a frustum of a cone, as it tapers from a larger diameter to a smaller one. The formula is:

[ V = \frac{1}{3} \pi h (r_1^2 + r_1 r_2 + r_2^2) ]

where ( V ) is the volume, ( h ) is the height, ( r_1 ) is the radius of the larger end, and ( r_2 ) is the radius of the smaller end. The dimensions of the reducer must be specified for accurate design and manufacturing.