Ring structures in singular instanton homology

We calculate the ring structure of the singular instanton Floer homology of $(S^1\times \Sigma, S^1\times \{p_1,\dots,p_n\})$ with C-coefficients, where $\Sigma$ is a closed oriented surface. As an application, we prove an excision formula for singular instanton homology when n=1. This settles the last unknown case of excision formula for instanton Floer homology.