Hi John Savas
 
Thanks for your question! 
 
The zip and link in a soft/medium or a medium/firm would mean that the mattress would have one of the tensions mentioned in each piece. There are no soft/medium or medium/firm spring tensions. These are to be paired up to the sleepers body weight and then from there your sleeping habits and personal preference will determine the overall style of mattress. 
 
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I hope this helps if you have any further questions please don't hesitate to contact the office on 0161 437 4419