Prototype Si microstrip sensors for the CDF-II ISL were fabricated by Hamamatsu Photonics and SEIKO Instruments using 4" technology. The sensor is AC coupled and double-sided forming a stereo angle of 1.207 degrees. The strip pitch is 112 mu m on both sides. The main differences between the two manufacturers lie on the technologies of passivation and the structure of coupling capacitors. We describe the design of the sensor and evaluation results of the performance. The evaluations include the total and individual strip currents and interstrip capacitance measured before and after Co-60 gamma irradiation. (C) 1999 Elsevier Science B.V. All rights reserved.