Instruct: Classify Amazon reviews into positive or negative sentiment
Query: on line purchase

The sunnto viper add said it was 0-100% o2 compattible sunnto site said 0-50% so this was a descrepancy I found buyingWell I ordered 2 and did not get a working unit they did give a refund but what a pain had to wait for them to comfirm they recieved the order back and they were out of stock for a replacement this is the second time I have posted more than 20 words but I am sure a negative post is the reason they bounced the first review.