An improved ferrule spacer for use with high density fuel rod arrays within boiling water reactor fuel bundles is disclosed. Ferrules are constructed in mating ferrule pairs. Each ferrule is divided into upper and lower ferrule halves. One ferrule half has sides thereof with the walls removed. The other ferrule half has its in place. The ferrule pairs are confronted with one ferrule inverted with respect to the other and with each complete ferrule wall of one ferrule half being juxtaposed to a ferrule half at a missing wall. Preferably, and at the point of tangency between the ferrule pairs, an aperture for receiving and confining an "H" type double loop spring is defined. The disclosure includes ferrules having a circular surround for the fuel rods and ferrules having an octagon sectioned surround for the fuel rods. Each member of the ferrule pair is symmetrical and completely interchangeable to provide for both convenient assembly and a small inventory of assembly parts.