RCD #6 1 Gallon Mastic Bucket

Works great for covering small gaps and holes in your duct work. Pretty easy to spread with a 2 1/2 in paint brush. I let mine dry then covered it with some tin tape - belt and suspenders but it gives it a clean look.For some reason I could not find this particular type in the big-box stores. Not 100% sure why.Depending on your ductwork a gallon may be way more than you need. I have at least a 1/2 gallon left so I will be applying it to my in law's ducts.Big question: return on investment. Depending on the sites you read it goes from 0% chance to 3 years or longer depending on size of house etc. The "0%ers" say all your heat/cool dumps into your house anyway so you aren't loosing anything. My view is I want as much air sent to the locations it was intended to go. If you feel too hot or cold chances are you change the temp costing you more.

I used this mastic on my heating ducts in the basement to seal the small holes and potential gaps. You can lose a lot of energy and money due to holes in your basement heating ducts. Horizontal ducts are especially prone to holes. I alternated between directly applying it with a paint brush and putting it on top of electrical duct tape (don't use regular duct tape - it won't stay on).It seems to work great. Of course this is my first time dealing with heating ducts, but from what I've read this is a good solution.

Mask miles of HVAC joints with this stuff, stopped up all those nasty leaks. Building codes should require that all HVAC joints be smothered with this stuff. Don't let any HVAC contractor or anyone use "duct" tape on your system. That stuff is c*rp and a mess to remove later and do right. If a contract puts up any fuss and wants to use duct tape, tell them thank you but no thank you. A exception is true duct tape whis is essentially metal foil with glue on one side.

was doing a retrofit of my a_c system.didn't open kings for 4 or5 weeks after I received it .when I opened it was hard as a rock they will not accept returns.product must have been out of date. Don't buy

Arrived on time but was almost rock hard when I opened it. Strange 'cos the seal was intact. No amount of stirring made any difference to the consistency, so I simply returned it.

This stuff was really worth the purchase. I did all the vents and improved AC efficiency by at least 20%

Arrived as a dried out semi-solid.

awesome sauce... for sealing things especially heat ducts...