Results of a study of the influence of the lattice and element configurations on the performance of frequency selective surfaces consisting of arrays of simple tripoles and tripole loops are summarised. The performance indicator is the stability of the main reflection band centre frequency during the alteration of the state of incidence of plane EM waves. Most of the results, presented graphically in terms of the percentage drifts as functions of lattice angles or element separations, refer to incidence from 0° to 45°, although some data are given for 80° incidence. Some lattices produce equal drifts for TE and TM incidence and some give very little drift at all for certain states of incidence. The simple tripole tends to give less stability than the tripole loop for which drifts of two or three percent are typical.