aimed using circular scales on the inside walls of the turret. The machine guns could not be placed in two adjacent ports; there always had to be at least one port between the two gun positions. The ports were closed when not in use by universal ball joint locks (Kugelkalottverschlüssen). The gun mounts had a matching ball head that sealed the ports when the machine gun was in its firing position. The six-port turrets were of Type 20P7, had an average wall thickness of 255 millimetres, an inside diameter of 2.25 metres and a weight of 51 tonnes. Their overall height was 2.64 metres, of which only 1.34 metres projected above the roof of the bunker. Due to their effective range of 1,650 metres, the machine guns in the turrets could be seen as the "long distance weapons" of the bunker; in particular, they could cover the opposite bank of the River Saar and the hillside that climbed away from it. The M 19 grenade launcher was intended for close-quarter defence. It had a range of between 20 and 600 metres and could in theory fire up to 120 50mm grenades per minute. The grenade launcher was built into an armoured Type 424P01 turret, which only projected 0.50 metres above the top of the bunker. The turret had a weight of 26 tonnes, an inside diameter of 1.70 metres, an overall height of 2.63 metres and an average wall thickness of 250 millimetres. The fortress flamethrower was known as a Festungs-Nahkampf-Gerät, a fortress close quarter combat device. It was intended for the defence of the top of the bunker and the immediate surrounding area. Its maximum range was 40 metres and it could last up to 90 seconds, using 120 litres of oil. The flamethrower worked at a pressure of 20 atmospheres which was created in a special pressure cylinder. The pressure vessel was filled from a container that held 2,500 litres of oil. The device took two minutes to prepare for firing (filling the pressure vessel and building up the pressure). The ignition of the oil was achieved using acetylene gas. For observation and fire control the commander had a Type 90P9 observation cupola. Through 5 slits, that could be closed by slides, the commander could observe the surrounding area and direct fire using two armoured periscopes. The cupola had a weight of 6 tonnes, an average wall thickness