A core unit for a heat exchanger comprises a pair of headers spaced from one another each defining a fluid space for receiving a fluid therein and each defining a plurality of apertures. A first region comprising a plurality of first tubes extends between the headers and a first fin is disposed between adjacent pairs of the first tubes. A second region comprising a plurality of second tubes extends between the headers and a second fin is disposed between adjacent pairs of the second tubes. A crushable center different than the first and second regions is disposed parallelly between the first and second regions for controllably crushing when the headers are bent.