In reply to JonmapDL:
be very careful here with ryanair. the bouldering mat will be classed as sports equipment. there fore you will have to pay a sports equipement charge. next all your under the airplane luggage must not exceed 15kg. combined. this is to say if you want to put 5 bags under the plane the weight of the 5 added together must not exceed 15kg. so thats 3kg per bag. it is not 15kg per bag its 15 kg for all bags together.