One fleet concept you see a lot of in low sec these days (and maybe other areas, I'm ignorant of the current meta out there) is Tech 1 armour cruiser fleets. These fleets are often based around the formidable Vexor hull with short ranged blaster damage and long range drone damage, supported by a handful of Atrons for fast tackle, Maulus or Celestis for sensor dampening, and Exequror or Augor logistic support.
Its a solid fleet concept. However, as you get to larger sizes (i.e. 10+ ships) there is one hole that needs filling (innuendo intended!). A ship faster than the slow armoured Vexors but more durable than the light and vulnerable to drones Atrons, a ship that can be second-man-in and make and hold a tackle in adverse scenarios long enough for the fleet to support.
The Heavy Tackle Armour Thorax:
|Click to Embiggen|
If you fly in low sec, using some low grade