galilean loupes 2.5 x is the most popular model. It offers the widest field of view and longest depth of focus. It has excellent clear view and great optical capability to provide the operator with the optimal magnification while providing extended field of view Items: 250S, 250R, 250L, 250XL Power: 2.5X Working distance: 340mm(S),420mm(R), 500mm(L),550mm(XL Depth of view: 80mm (S); 90mm (R); 110mm (L); 120mm(XL) Field of view: 90mm (S); 100mm (R); 110mm (L); 120mm(XL) Weight: 42g Frames: Ni-alloy or Titanium 3x is designed for persons that need more magnification, it also offers comfortable frames with adjustable gel nose bridge Items: 300S, 300R, 300L, 300XL Power: 3.0X Working distance: 340mm(S),420mm(R), 500mm(L),550mm(XL Depth of view: 60mm (S); 80mm (R); 90mm (L); 100mm(XL Field of view: 90mm (S); 100mm (R); 110mm (L); 120mm(XL) Weight: 48g Frames: Ni-alloy or Titanium 3x is designed for persons that need more magnification, it also offers comfortable frames with adjustable gel nose bridge Items: 350S, 350R, 350L, 350XL Power: 3.5X Working distance: 340mm(S),420mm(R), 500mm(L),550mm(XL Depth of view: 60mm (S); 80mm (R); 90mm (L); 100mm(XL) Field of view: 55mm (S); 60mm (R); 65mm (L); 70mm(XL)L) Weight: 52g Frames: Ni-alloy or Titanium