DC50 5 LB Duct Seal Compound

Shipped fast, quality is good and a lot of it. Used for sealing the lines around a cars expansion valve and lines to the evaporator.

I am using this as a stop for stopping the forward movement of lead. From air pellets going over 1000fps to subsonic centerfire rounds (,1050 fps), if you have enough of this, it will stop the forward movement. I would wear gloves and try and make a cube if at all possible. It is very sticky and will stick to anything it touches. It will get dirty and caked with lead so cleaning it will be crucial.

I use it for a back stop when I shoot my high powered pellet rifles indoors.

I'm no HVAC expert, just a typical homeowner, but this was the best price for the largest amount I found while browsing Amazon. It's more than you think based on the picture, it's a large "slab" of this material. Handles like a thick slightly sticky hard playdough. Pull off a chunk and shove/work it into any gaps or holes in your HVAC system.Only thing I've noticed, and it's not really a downside, is it seems like it's a pretty poor insulator. But I don't think it's made for that, only to block airflow. Just be aware of that if you hope it's going to insulate as well as seal.