Abstract: To prevent a supported block, particularly a ring laser block, from translating, rotating, or being stressed with changes in temperature, the block to be supported carries a plurality of, typically four, coplanar radially-outward-extending circularly cylindrical posts. The posts are grasped by compliant axially-split sleeves or mounts which engage posts. The mounts are supported by a surrounding substantially circular frame. The mounts are substantially equiangularly positioned around the frame, and the posts are correspondingly positioned upon the block. The frame is surrounded by a case which is adapted to be fastened to another structure such as a vehicle or gimbal. At points angularly positioned around the frame, substantially equiangularly positioned from the adjacent sleeve fixtures, the frame is rigidly attached to the case. The mounts and the frame are both made of a material, typically Invar, having a known temperature coefficient of expansion.