The Glock G20 Gen 3 was introduced in 1998 and featured an integrated accessory rail known as the Universal Glock rail. Other upgrades of this polymer-framed pistol included thumb rests on both sides of the frame and finger grooves on the front strap. Glock later improved on the G20 Gen 3 further by adding a modified extractor that doubled as a loaded chamber indicator as well as an enlarged locking block and an extra cross pin.