From Lexicanum

The Protector is the Tau's main fighting vessel and the last of the fleet renovation program. They are designed and built with the purpose of engaging and destroying the enemy in fleet action. This class saw action for the first time in the Taros campaign and inflicted heavy loses on the Imperium's transport ships.

The size of the Protector is roughly the 1/2 of an Emissary Class cruiser. It can transport up to 2 squadrons of Barracuda or Manta.Although it is not as bulky as the rest of the cruisers it has comparable firepower and can fight Imperial cruisers on even terms.

Sources

Imperial Armour Volume Three - The Taros Campaign

Kor'vattra - Tau Navy

Type	Design	Class
Capital Ships	Battleships	Gal'leath - Explorer • Or'es El'leath - Custodian
	Cruisers	Il'fannor - Merchant • Lar'shi - Hero • Il'Pourri - Emissary • Lar'shi'vre - Protector
Escorts		Kir'qath - Defender • Skether'qan - Messenger • Kass'l - Orca Gunship • Kir'la - Warden Carrier Escort • Kir'shasvre - Castellan Heavy Escort
Attack Craft	Fighters & Bombers	Manta Class Bomber • Barracuda Class Fighter • Remora Drone Stealth Fighter‎
Mercenaries & Allies	Kroot Vessels	Warsphere
	Nicassar Vessels	Dhow
	Demiurg Vessels	Stronghold Class Commerce Vessel • Bastion Class Commerce Vessel