A comprising includes one or more polyethylene, one or more polypropylene, one or more polyolefin elastomer, and a crystalline block composite having the following three components: (i) a crystalline ethylene based polymer, (ii) a crystalline propylene based polymer, and (iii) a block copolymer having a crystalline ethylene based block and a crystalline propylene block. The composition of component (i) is the same as the crystalline ethylene based block of the block copolymer and the composition of component (ii) is the same as the crystalline propylene block of the block copolymer. The composition is useful for forming rotomolded articles.