XS Sights Big Dot Tritium - S&W J Frame & Ruger SP101 (fixed rear)XS Sights Big Dot Tritium S&W J Frame & Ruger SP101 (fixed rear) The XS Big Dot tritium night sight is a superior defensive sight. Fits S&W J Frame with pinned front sight and Ruger SP101 with a fixed rear. Precision machined in Fort Worth, TX, XS Sights feature a Big Dot Tritium front sight for fast sight acquisition in all light conditions. Big Dot demands your attention even in high stress and for those with poor eyesight, aids in rapidly achieving