Heat transfer and flow friction design characteristics are presented for some “second-generation” glass-ceramic heat exchanger surfaces. These surfaces are of interest in their application as the matrix for the rotary regenerator of the vehicular gas turbine engine.The paper gives the results for four test matrices, with 550-1650 ft2/ft3 area densities. Two matrices had hexagonal cross-sectional passages and two had circular passages. Test results, derived by the single-blow transient technique, are compared with predictions from laminar flow conduction theory. Flow Reynolds numbers are in the range 80 < Re < 1000.These surfaces have some advantages over the currently employed triangular passage geometry. The significance of these advantages in terms of the regenerator thermal performance and envelope geometry is discussed.