A high intensity discharge lamp (10) has an outer envelope (12) having a cup-shaped top (14), a hollow center section (16) and a bottom (18) all aligned along a longitudinal axis (20), the bottom (18) including a flare (22) having a pinch seal (24) with in-leads (26, 28) sealed therein. A mount structure (30) is positioned within the envelope, the mount structure including a frame (32) comprising a spaced-apart pair of side frames (34, 36) extending substantially the length of the envelope (12) and parallel to the longitudinal axis. The side frames (34,36) have middle portions (35,37) carrying an arc tube (38) and a surrounding shield (40), and the side frames further have an upper portion that frictionally engages the inside surface of the cup-shaped top (14), the upper portion comprising two ends (42, 44) extending in a direction normal to the longitudinal axis and having a space (50) therebetween.