GTS550 5 Stage RO 6 & 12month service kits and Membrane Replacement Kit.
6 month kit includes:
1 x Sed 10/5 Filter
1 x Sed 10/1 Filter
1 x GAC10 Filter
12 month kit includes:
1 x Sed 10/5 Filter
1 x Sed 10/1 Filter
1 x GAC10 Filter
1 x GS10J Carbon/polishing filter
R.O. membrane - see (link)
recommend replacement every 2-3 years 
