Medium Firm is the level of support to the body, suitable for average to heavily weighted people. This is not a comfort rating.
Open Coil are Bonnel springs in an hourglass shape, joined creating an open coiled mattress.
Fibre Fillings fillings are 100% polyester, man made, very durable, great recovery.
Source 5 Domestic Flammability Rated BS 7177 Medium Hazard, Hotels, Universities, Holiday Camps, Retirement Homes.
Mattress Depth 25 cm
Pillow Top effect, that looks separate to the mattress but is actually attached with a hidden return, usually has soft fillings.