For double-frequency coils, it has been shown that four-ring birdcage coils provide minimum losses at X-nuclei frequencies. However, to avoid coupling between two rings, the length of the outer parts needs to be extended, increasing the unusable area at the service-end. In this study, we redesigned one side of the conventional birdcage coil as a dome shape by using end-caps. The domed birdcage coil was evaluated in simulations in both the single- and double-tuned condition. The performance of the folded-ring, domed and double-tuned birdcage coil was also evaluated and compared to that of a conventional single-tuned birdcage coil.