I purchased my t-cell through Amazon.com. I have a 7 year old Nature Soft system that really has served me well. The t-cell finally failed, two years after its normal life span. Not bad. I live in Florida so the system runs 365 days a year at around 8 hours per day. Do the math.
Buying the replacement t-cell through Amazon saved me almost $180.00 - no complaints there. I ordered it on the 13th of the month and it arrived on the 18th of the month - super saving shipping and it came 4 days earlier than estimated. Again no complaints.
I removed the old cell, making sure my pool water was chemically balanced, and installed the new cell. Turned on the pump, reset the controller, and I've got chlorination again.
My only mistake I made was not checking the salinity of the water with salt strips before adding more salt because the controller displayed low salt. When the cell is older than 3 years, double check your salt level with salt strips before adding salt. I added so much salt before realizing the cell could be bad, that I needed to drain almost half the pool and refill with clean water to get the level back into the normal range.
One other thing that may be of useful information is that you should replace your cell with the same rating as the one that has failed. I have a 13,000 gallon pool with a 40,000 gallon t-cell. I could have gone with a lower rated t-cell, but then I think one needs to change the firmware to adjust for the difference. With the exact replacement cell, you only need to reset the controller after reinstalling the new replacement t-cell.