Anyone care to share what is the best age to learn abacus? And any recommendations?

I only just started my boy at CMA this year which he's in K2. I would actually recommend to start him earlier maybe around K1? Of course the child have to know basic numbers and understand instructions first before you can consider sending him/her to classes else it would be quite waste of money. Anyway just send your child to their trial and see if he/she likes it? My boy loves it since the first day of trial. If you need any referral, kindly let me know. There's a small discount for referral student.