# Bit-Vector Extension by Proxy References **DO NOT** use this. You *clearly* have a bit-slice. Use [`.extend_from_bitslice()`] instead! Iterating over a bit-slice requires loading from memory and constructing a proxy reference for each bit. This is needlessly slow; the specialized method is able to avoid this per-bit cost and possibly even use batched operations. [`.extend_from_bitslice()`]: crate::vec::BitVec::extend_from_bitslice