Concurrent data structures often provide better performance on multi-core platforms, but are significantly more difficult to design and verify than their sequential counterparts. The C/C++11 standard introduced a weak language memory model supporting low-level atomic operations such as compare and swap (CAS). While these atomic operations can significantly improve the performance of concurrent data structures, programming at this level introduces non-intuitive behaviors that significantly increase the difficulty of developing code. In this paper, we present \TOOL, a specification language checker that allows developers to write simple specifications for low-level concurrent data structures that make use of C/C++11 atomics and check the correctness of concurrent data structures against these specifications. \TOOL is designed to be used in conjunction with model checking tools and we have implemented it as a plugin to \cdschecker. We have evaluated \TOOL by annotating and checking several concurrent data structures.