Older Mono spas have the 5cm child proof locks  welded to the liner. The manufacturer is no longer producing any product with the 5cm child proof locks. The new verto series - mono-eco 6, 8 and Tidal all now have the 3.8cm buckles. If you need a replacement liner for your old pool, you will also need to putrchase a new cover with the 3.8cm  

Mono 6 Pool Liner. This is just the shell for the MSpa, it does not include any inlet or outlet valves, or the cover. these are all available to purchase separately

SS26 Frame F-MO062WE  pool liner (3.8cm webbing Female buckle)， match to use with B9302171 SG (pool cover) if replaced B9301537+B9301376

PART-B9302170SC