An impact attenuating device includes both concave and convex side walls, e.g., in an interleaved arrangement, optionally at least partially surrounded by a restraining element that may help return the impact attenuating device back to its original orientation after attenuating an impact. Such impact attenuating devices may be included in pieces of footwear and/or other foot-receiving devices. Additionally, such impact attenuating devices or portions thereof may be freely selected and/or interchanged in a piece of footwear or other foot-receiving device, e.g., based on one or more characteristics of an intended user and/or an intended use, so as to allow users to obtain footwear (or other devices) customized and targeted for use under a predetermined set of conditions.