It is optional... doesnt mean it wont be applied to AK... again its roof is very well armoured... it has era on roof and its armour is thickened with AV-8 Kevlar... it has much thicker armour than any other mbt in service including T-80UD... as for turret redesigning the AK-II will have it... also it as :
CREW BAY EXPLOSION, DETECTION AND SUPPRESSION SYSTEM
A military vehicle is designed for strength, its armour affording protection to the crew and giving them the confidence to perform in battle. But the possibility remains that penetration of its fuel tanks or fuel and hydraulic lines can lead to a devastating fireball, causing severe burning and toxic gas poisoning within milliseconds. This threat inevitably affects crew morale and it is therefore important to give the crew a means of surviving in the battlefield environment. The crew bay system is able to sense the incipient hazard and recognise it as an explosive fire within 2-3ms and to effect complete suppression in approx 100ms. It uses fast response sensors and rapid acting high-rate discharge suppressors. Because suppression has taken place in a few tens of milliseconds, the radiation from the fireball is harmless, the temperature rise is minimal, the pressure increase is survivable and, most importantly, the amount of toxic gas generated is limited to safe levels. The vehicle and crew have survived to fight another day. Crew bay systems are fitted to a range of vehicles including Leopard 2, CRARRV, Tariq, Al-Khalid, Marconi Marksman, T90, Leclerc, M1A1, M1A2, LAV25, C1 Ariete MBT and Chunma amongst others.
Il reply to ur post later .. gotta go...