How big can my checked baggage be?

Hi everyone!

I've just bought a ticket to Dublin and I need to know what's the size for the checked baggage. I know it can't be more than 15 kilos but how big?
I'm asking this because I know Ryanair have restrictions with hand-baggage is not the same with the checked baggage?

Any help would be greatly appreciated!

Thanks!!

Tha answer is in

http://www.ryanair.com/en/questions/checked-baggage-allowance

Excerpt :

Can I carry Excess Baggage?
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Any passenger exceeding their checked baggage allowance per bag will be charged for the excess weight at the applicable rate per kilo. Please note that each passenger can pay for a maximum of 2 checked bags each bag must each bag must not exceed its maximum bag allowance.
For health and safety reasons Ryanair does not accept for carriage any individual item exceeding 32 kilos or with combined dimensions ofmore than 81cms (height), 119cms (width) and 119cms (depth). This weight limit does not apply to mobility equipment.
If you are planning to travel with excess baggage, we suggest you arrive at the airport 2 hours prior to your scheduled departure time.