Tuff Twins

Tuff Twins is a boss added in The Binding of Isaac: Repentance that can appear in.

Behavior
Tuff Twins always spawn in a pair consisting of 5 body segments and a head segment each. They are always fought in a double-sized room.
 * The Tuff Twins roam around the room randomly, like Larry Jr.
 * Normally invincible, but bombs and explosives can destroy their stony exteriors (after 15 damage per segment), making their segments vulnerable.
 * There are always at least two Bomb Grimaces that dispense Red Bombs for Isaac to use against the Tuff Twins.
 * Head segments spit Inks while protected by its rock armor.
 * Vulnerable head segments, spits Suckers instead.
 * Vulnerable body segments, spew bloody shots similar to Boils.
 * When a flesh segment is killed it spews blood shots.
 * Tuff Twin segments can be split into smaller copies of the boss as long as the new Tuff Twin segments are longer than 2 pieces.
 * The Tuff Twins become faster the more rock armor they lose.

Trivia

 * They appear to be a rocky variation of Larry Jr.
 * The Shell appears to be the posthumous version of them.
 * Tuff is the name of a type of rock formed from volcanic ash.