A downhole isolation tool includes a mandrel made of non-metallic material, the mandrel comprising an isolation region at a first end of the mandrel, a shear sleeve adapter disposable on an outer surface of the isolation region, the shear sleeve adapter having holes aligned with holes in the outer surface of the isolation region, a slip assembly positioned around an outer surface of the mandrel, a packing element positioned around the outer surface of the mandrel, and a shoe positioned around the outer surface of the mandrel at a second end of the mandrel.