Vassa is a basic practice for Buddhist monastics. During this three-month retreat, monks seclude themselves and follow a tight regimen of meditation and dharma study. Every year, the Insight Meditation Society runs a three-month course that has been called the "marathon of meditation". Save for triweekly interviews with instructors and nightly lessons, the retreatants observe full silence. In Theravada tradition, after lunch, they do not eat another meal, but are allowed snacks and drink tea, which is not accepted by many Buddhists as proper practice. The center's courses provide instruction and practice in vipassanā or mettā meditations.