An in-line button drip emitter may include a core fitting into a cover. For example, the core may include a cylindrical section with an elliptical cross section. For example the cover may close over a pressure reducing labyrinth formed in the outer cylindrical sides of the core. Optionally the cover has a long axis which is parallel to the long axis of the cross section of the core. In some embodiments, the bonding surface has an arched profile. Optionally, the arched profile fits an inner wall of an irrigation tube. For example, an axis of the arched profile may be parallel to the long axis of the elliptical cross section of the core and/or the arched profile may be parallel to the axis of the cover.