The 28,000-dwt newbuildings will be built at Hudong-Zhonghua Shipyard for delivery in April and August 2018.
The options were attached to an order for four sister vessels ordered in January this year as part of a total package worth $280m.
Coscol said the class of vessels will feature twin cranes with a combined lifting capacity of around 700t.
Principle particulars of the vessels include a length overall of 179.5
