Abstract: A hay baler includes a compression stage having a first major wall conveying device, a support surface, a first sidewall conveying device and a second sidewall conveying device which are arranged to form a compression chamber and driven at compatible speeds to propel hay toward a downstream end of the compression stage. The first and second major wall conveying devices are in spaced relation to each other. The first and second sidewall conveying devices are transversely oriented and form first and second side walls of the compression chamber and are angled so that the compression chamber tapers from an initial width at the upstream end to a smaller final width at the downstream end.