I can't remember what SR stands for, but I do know that Meade sends these little refractors Kellner eyepieces. Did you get a 12.5mm too? These are .965" barrel size eyepieces. This scope should have come with a 1.25" adapter for larger eyepieces. It should screw on the end of the focuser. The .965" eyepieces smaller that 18mm are virtually worthless. The feild of view is so small that it is almost impossible to see through. If you do have an adapter for 1.25", then you'll have to buy eyepieces in 1.25" barrel size. If you do, get plossel type pieces. 26mm and maybe a 17mm or 12.5mm. Get the 26 or 25 first. Larger field of view and better eye relief. If you have a 3x barlow, it will not work well with a 4mm. Good Luck!!