The invention provides a carbosiloxane vinylic monomer which comprises one sole ethylenically unsaturated group, one sole terminal butyl group; and one oligo(carbosiloxane)-containing linkage between the ethylenically unsaturated terminal group and the terminal butyl group. The present invention is also related to a polymer, an actinically-crosslinkable silicone-containing prepolymer, a silicone hydrogel polymeric material, or a silicone hydrogel contact lens, which comprises monomeric units derived from a carbosiloxane vinylic monomer of the invention.