Initially I thought the normal setting jet spray at 100 psi was too strong but it is true that your teeth/gums quickly get used to it. I have been using it several times a day for about a month and would DEFINITELY recommend this product. My teeth appeared whiter after 2-3 weeks. I also practice coconut oil pulling which also whitens teeth and I wasn’t expecting further whitening affect. I always had yellow tinge on the sides of top molars for years and years and read that residual plaque/biofilm will cause this yellow tinge. So happy that water flossing has completely removed the tinge. It is true that no matter how diligently I brushed I always noticed tiny traces of biofilm at gum line but not so after using this water flosser. The size is convenient for traveling although I have to refill the chamber (even for 1 session) I don’t mind because it means I can gradually increase the water temperature for the subsequent session(s). I am very pleased with this product and am even considering buying a second one to leave/use at the office.
UPDATE June 25, 2018. I have reduced my initial 5 star rating to 1 star because it has stopped working effectively after only 8 weeks. The power behind the water jet just suddenly diminished (mid-use) and no longer cleans. Like most people, I HATE wasting my money on a product that just works fantastically for 2 months! Not good and not fair on the consumer.
UPDATE June 28, 2018. I put my rating back to 5 stars (from 1) solely because this sellers customer service is EXCELLENT. My device worked well for about 2 months and then just started to emit a weak water jet/spray that wasn't cleaning teeth at all. I hope my device was just a rogue one but I can tell you that the seller immediately contacted me and provided a refund. I sense they care about receiving honest feedback, will attempt to address such rogue occurrences and care about their customer-satisfaction. Many thanks to them.