Of the four types of bomber used by the "Luftwaffe" the Ju 88 (the original "Schnellbomber") was considered to be the most difficult to shoot down. As a bomber it was relatively manoeuvrable and, especially at low altitudes with no bomb load, it was fast enough to ensure that a Spitfire engaged in a tail-chase would be hard pressed to catch up. It could carry up to 3,000 kg of bombs. However, only small sized 50 and 70 kg bombs, up to a total weight of 1,400 kg, could be carried internally, while larger bombs had to be carried on external racks, causing considerable drag. The Ju 88 was also extremely versatile, being fitted with both the Lotfernrohr 7 gyroscopic bomb sight and Stuvi dive sight as well as retractable dive brakes. The front MG 15 machine gun could be locked with an ingenious retracting clamp just forward of the windscreen to lock it for forwards firing, and could be used for strafing runs. Thus the Ju 88, dubbed as the "Big Stuka", was equally at home when it came to level or dive bombing or low-level attacks. The versions of the Ju 88 used during the battle were the small-wingtipped A-1 and the A-5; the latter incorporated several improvements, including the A-4's increased 20.08 meter wingspan and uprated armament. The Ju 88 C-1 heavy fighter version, with a sheet metal nose replacing the bombers' "beetle's-eye" faceted glazing, was also used in small numbers.