The Zaffiri Precision HD Sight Set are high quality steel, not hollow. They have a set screw on rear and a stainless front screw - features you won't find on competitors at this price. Front Sight uses standard hex driver. Rear Sight uses 1/16a ^2 Allen wrench for set screw.Standard height sight set (NOT Suppressor Height) IncludesFront Sight: 0.195a ^2 Serrated Tall and Stainless Steel screw 1.5mm Red Fiber OpticRear Sight: 0.200a ^2 Serrated Tall with 0.125a ^2 Wide notch featuring shortened front ledge that will fit slides for an optic6-40 x 1/4a ^2 rear set screw DISCLAIMER: This product is not manufactured, authorized, endorsed, or warranted by GLOCK. GLOCK does not warrant or represent that this product is compatible with GLOCK pistols.