They can be used for flue gas, ventilation ducts, etc. Designed to protect pipes from precipitation, as well as to increase traction.
eBay
Black Silicone Rubber Hole Caps 2.5mm-50.6mmSeal Stopper Snap-on T Type Plug Cover Gasket Blanking End Cap
Aliexpress UK
Chimney Pipe Cowl. Stainless Steel for Good Weather Resistance. Wall Thickness - 0.5mm. Ø 180 mm / 7.09". Ø 160 mm / 6.30". Ø 150 mm / 5.91". Ø 140 mm / 5.51". Ø 125 mm / 4.92".
eBay
8/24pcs Pipe End Blanking Caps Bung Tube Insert Plug Round Plastic Blanking End Cap Diameter14/16/19/22/25/30/35/40/45/50mm
Aliexpress UK
Item Type: Chimney Rotating Ventilator Cap. Venting Effect: Provides optimized venting performance, improves combustion efficiency, and reduces the of chimney build‑up and backflow. Safety: Effectively prevents small animals and rainwater from entering the flue, protecting the integrity and function of the chimney.
eBay
Silicone Rubber Hole Caps Blanking End Caps Pipe Tube Inserts Plugs Dustproof Bungs WHITE & BLACK, size A=6.8mm~201.5mm optional
Aliexpress UK
Birdguard and chimney pot cap cowl for keeping out rain and birds like Jackdaws. ONLY connects to chimney pots (will not connect to any kind of flue pipe). SEE PHOTOS FOR SIMPLE FITTING INSTRUCTIONS.
eBay
10-50pcs PVC Rubber End Caps, 3-25mm Threaded Pipe Caps, Steel Plastic Pipe Protector Tips, Assorted Size Kit
Aliexpress UK
Simply place it over your chimney flue and enjoy knowing your chimney is protected. Stay worry-free and keep your chimney in top condition with this chimney cap. 1x Fireplace Chimney Cap. Garden Structures & Shade.
eBay
1PC Bathtub Shower Faucet Handle Accessories Mixing Valve Pull Brass Pull Cap Water Divider Pull Cap Handle
Aliexpress UK
Universal fitting, simply squeeze the legs into your existing chimney pot. Designed to fit chimney pots between 8" (200mm) and 10" (250mm).
eBay
316 Stainless Steel 22mm 25mm Bimini Top Fitting Marine Hardware Slide Cap Slide Jaw Sleeve Pipe Eye End Cap
Aliexpress UK
Designed to prevent rain, birds, vermin and leaves entering used or unused chimney flues. this cowl is suitable for woodburning, solid fuel and oil burning appliances This product provides good ventilation and gives protection against wind and rain.
eBay
4pcs PVC Handrail End Cap Round Stair Treads Cover Fittings 45mm Handrail Stair End Cap Wood Rail Sealing Covers Plugs
Aliexpress UK
Chimney Bird Guard, protects your chimney from nesting birds, features a rain cap to prevent rain traveling down your chimney, also preventing a back draught into your fireplace. Steel construction yet can be easily squeezed or stretch to fit your chimney pot.
eBay
Sink Overflow Ring Cover Bathroom Sink Hole Cover Basin Trim Cap Bath Sink Drain Cap Wash Basin Plug Bathroom Accessories
Aliexpress UK