In Tantric ritual the vajra is ofte

In Tantric ritual the vajra is often paired with the bell (ghanta). Together, they are considered as complimentary parts, like male and female aspects of the universe (for comparison, consider yin and yang, and so forth).

These two instruments symbolize the two most essential components of Mahayana doctrine: the vajra represents skillful means (upaya), while the bell represents wisdom (prajna). Both of these aspects of Mahayana / Vajrayana are necessary to live as a bodhisattva.

One needs the wisdom of understanding the ultimate emptiness of all things, but at the same time the skillful means of being able to help all sentient beings because they suffer in samsara.

In practicing Vajrayana, the Tantric practitioner (called a “tantrika”) develops both skillful means and wisdom in himself until he becomes a bodhisattva.