A feature in modern graphics cards that ensures only full video frames are rendered within one monitor refresh cycle. Video games exhibit varying action, and modern graphics cards can render a variable number of frames per second. Vertical sync (Vsync) eliminates "tearing," in which horizontal sections momentarily appear offset from each other when two sequential frames are rendered in the same refresh cycle. However, with Vsync turned on, time differences between the video frames and monitor refresh cycles can cause the same frame to be displayed twice, creating a brief hesitation ("stuttering"). See adaptive sync and tearing.