It’s the inside of a used, non-charged coolant filter, which is the same Baldwin unit used in my ’97s coolant filtration kit. Man, can your coolant system get contaminated! It's amazing that factory water pumps last as long as they do! I’m really glad we installed DieselSite’s coolant filtration system on my truck when we changed the water pump last year.
With all of this sand and debris running through your cooling system, it’s good peace of mind knowing most of it is being caught before it can do any damage. After 19,000 miles on my first filter, I changed it out last Friday. I’m going to cut it open soon to take a peep inside.