mount. Six Sd.Kfz. 251/16 Flammpanzerwagens were authorised for issue to each Panzergrenadier regiment or in the Pioneer battalion. Though vulnerable, they were used very successfully at night to quickly attack enemy infantry who had just captured German trenches, hitting the enemy before they could consolidate and bring up the heavy weapons that would make them much costlier to defeat later. Late ausf. D versions had larger gunshields. Sd.Kfz. 251/17 - Schützenpanzerwagen (2 cm). Anti-aircraft vehicle armed with a 2 cm KwK38 on a pedestal mounting with a small armored turret to protect the gunner. Late war, it was issued as a platoon commander's vehicle to replace the Sd.Kfz. 251/10. Sd.Kfz. 251/18 I - Beobachtungspanzerwagen. Artillery observation vehicle. 251/18 Ia - Differences unknown, likely different radio fit. 251/18 II - Armored observation vehicle. 251/18 IIa - Different radio. Sd.Kfz. 251/19 - Fernsprechbetriebspanzerwagen. Telephone exchange vehicle. Sd.Kfz. 251/20 - Schützenpanzerwagen (Infrarotscheinwerfer) Introduced in late 1944, it mounted a 60 cm infrared searchlight with a range of 1.5 km for illuminating targets at night. Known as "Uhu" (Eagle Owl), they guided IR sight-equipped Panther tanks to targets that were out of range of their own smaller infrared searchlights. Sd.Kfz. 251/21 - Schützenpanzerwagen (Drilling MG151s). Anti-aircraft and ground support variant equipped with a triple-mount ("Drilling" in German means "triple") of MG151 autocannon; early version being MG151/15 mm cannon, later being MG151/20 mm Luftwaffe cannon, on a Kriegsmarine triple mount. Strong firepower, especially when organised into platoons of 6 SPW. However, with a combined rate of fire of 2000 RPM, it could fire off its full load of 3000 rounds in just 90 seconds. Sd.Kfz. 251/22 - 7.5 cm PaK40 L/46 auf mittlerem Schützenpanzerwagen. Fitted with a 75 mm PaK 40 anti-tank gun. Probably too big a gun for the carriage, overloaded but effective, and the Yugoslav military was still using captured examples into the 1950s. Sd.Kfz. 251/23 - 2 cm Hängelafette 38 auf mittlerem Schützenpanzerwagen. Reconnaissance variant intended to replace the Sd.Kfz. 250/9 and fitted with the same turret mounting as the Sd.Kfz. 234/1 armoured car. Probably never built. OT-810 - Czechoslovakian modified version known as Tatra OT-810 was made by Podpolianske strojárne Detva. About 1,500 vehicles were built during 1958–62, they have had an air-cooled diesel engine made by Tatra and armored roof over the troop compartment for better protection in case of nuclear war. The vehicle was not liked by those who