HomeSaver's WindBeater Cap is a great, economical, lifetime warrantied alternative for preventing downdrafts.
If you frequently experience wind-related backpuffing, this cap could solve the problem. However, it won't cure non-wind related draft problems.
To attach the WindBeater to relining pipe, just slide the base inside the pipe as far as possible and secure with screws.
With solid-pack, class-A chimney with sealed ends push the cap into the sealed end chimney until secure. Silicone the joint where the chimney and cap meet.
The WindBeater is made of heavy, 24-ga., 304-alloy stainless steel, and is available in 3" - 12" diameters.
Small and large rectangular sizes and stainless adaptors for masonry flues are also available.