I went ahead and ordered the Kab Speedstrobe even though I had the strobe disc that was supplied with the SDS. Before the KAB arrived I thought I had my Scoutmaster platter speed set exactly at 33 and 1/3 but the KAB showed that the speed was fast by .07 on the SDS. So I'm glad I ordered the KAB, it's make's speed adjustment more accurate, plus easier and faster to dial in than the strobe disc that came equipped with the SDS.