1 major detrimental property.
The champion leather is armor that increases your damage by 27 of the attack damage once per round for a melee weapon. 

The breastplate and shoulder protectors of this armor are made of leather that has been stiffened by being boiled in oil. The rest of the armor is made of softer and more flexible materials.

Notes: Damage: Melee Weapon Attacks, Long rest by a fighter.