Does it fit mattresses 15 to 17 inches deep?

It will not fit a 15 or 17" mattress as it's a (9-12") mattress encasement. SafeRest does make a (12-15") and and (15-18"), which are also available on amazon.com. If your mattress is 15" or less get the (12-15"). If your mattress is greater than 15" get the (15-18"). It is very important to measure the thickness from the lowest point to the highest poofy part of the mattress. This will help you get the correct depth. If you need any help selecting the right size please call us at (866) 375-2323

Looking at this for dust mite allergy relief. What is the pore size of the mattress protector?

I have the same question: What is the pore size (in microns) of this cover?

My mattress is 12.5 inches. Will this work for me?

Yes, absolutely. Our mattress is a little over 12" and the cover fit and went on with very little effort. Later, we purchased a 4" memory foam mattress topper, with a cover. The cover for the mattress topper looked like such a "pain", we managed to fit it into our mattress cover.

Should the encasement fit snugly on the mattress to effectively kill bugs? Purchased the 15"-18" for a 16" mattress and mine is loose.

SafeRest offers encasements that are 6-9", 9-12" 12-15" and 15-18" thick. This close range of sizes ensures a good fit based on the thickness of your mattress. If your mattress is 16" you would have 2" of extra material on a 15-18", but that would not impact the performance of the product. The encasement doesn't kill bed bugs, but protects your mattress against bed bugs while reducing the areas where bed bugs may reside (tufts and folds of your mattress). Encasements are used as part of an integrated pest management approach to bed bugs including sprays, powders and Climbup interceptors.