I have just completed a test of crystals marketed by www.performancedevices.com I took one transmitter crystal and three receiver crystals and checked for range and any type of glitch that may happen. The range was equal/better than the original crystals designed for the radio. (KO PROPO EX-I) and totally glitch free. I used three different receiver crystals to make sure that the consistency from one crystal to the other was the same. I noticed no difference in performance from one crystal to the other. Considering that these crystals are about one half the cost of other crystals I would sure recommend them.