BUNA-N Tri-Clamp Tri Clover Gaskets Buna-N Tri-Clamp gaskets are the preferred choice of material when using a closed loop, closed column, or open blast extraction when butane or propane are used as the extraction solvent. Buna-N Gaskets offer a lower temperature rating and have better physical properties than Viton gaskets and the best part is that they are also cheaper than Viton and provide the same chemical resistance to butane and propane. ***Note: Buna-N is not recommended for use with | BVV BUNA-N Tri-Clamp Gaskets.