Mark 4 6.5-20x50mm ER/T w/ Holland's M1 Knobs FFP This is a first focal plane scope, allowing you to use the reticle on any magnification setting. This scope features a 30mm main tube and 50mm OBJ bell for excellent light transmission. Mark-4 dials have been greatly improved, with bigger, bolder numbers. If you need more magnification in a first focal plane scope, this is an excellent choice. We use this scope on all of Holland's training rifles at the Holland's Long Range Shooting School due to its versatility. This scope is the choice of military/law enforcement shooters around the world.