I discovered l had a rat problem under the floor of a mobile home l was working on in late March, 2019. I went thru 8 pounds of Selontra in 3 sations of 3 baits each in about 2 months. No let up in consumption. When that ran out l ordered a 16 pound bucket of Contrac thinking the high percentage of anticoagulant might be the way to win the war. Presumably, success in a rat eradication program would be an initial acceptance of the bait followed by a steady reduction of consumption, and reduction of other signs of activity. Acceptance was off the charts. The 16# bucket is now light. Eventually l duobled and even tripled the nightly dosage thinking l was still at a sublethal rate. Rodents love this stuff. Even if rats were coming from miles around in the time frame here l should have been tripping over 90+ dead rats. I never saw or otherwise detected any. Recently l added new stations and Fastrac Blox while still using Contrac sachets as a lure. (Rat people aren't the best spellers!). It's de-bait-able (oh boy) whether rats perfer old bait in new stations or new bait in old stations. Early results look like the nerve agent in Blox is doing some damage but they like Contrac better. One conclusion on Contrac: when it came off the hot Fed Ex van the contents were very oily and soon covered my rubber gloves when loading the stations. Keeping the bucket in the "beer fridge" solidified the oil and handling the sachets with a dedicated pair of long nose pliers solved that problem entirely.