They can be used for flue gas, ventilation ducts, etc.
eBay
2mm to 60mm Silicon Rubber Hole Caps Rubber Male Plug Silicone Stopper Tap Bung Plastic Pipe Seal Caps Cover Waterproof
Aliexpress UK
Disused Chimney - Strap Fix. Anti-Down Draught Bonnet Cowl. Terracotta and Buff. This cowl is great if you want to stop birds from nesting inside/on your chimney. Not only does it do the job you want it to do, it looks stylish too.
eBay
Thickened PVC Inner Blocking Cap Sewer Pipe Protective Cover Insert 50-160mm PVC Inner Plug Pipe Cap Lower Water Pipe Cover
Aliexpress UK
They can be used for flue gas, ventilation ducts, etc.
eBay
Black Silicone Rubber Hollow Stopper Plug Sealing Hole Caps Dust Plugs Pipe Tube Inserts Bungs Blanking End Cap
Aliexpress UK
The cowl is made of stainless steel sheet, which ensures high strength and excellent ability of the product to deformation.
eBay
1/5/10/50PCS 3-80mm Black Silicone Rubber Round Caps Dustproof Sealing Cap Steel Pipe End Cover Round Pipe Insertion Plug
Aliexpress UK
Upgraded Durability: Made of stainless steel, our rain cap is designed to keep your chimney debris-free and well-protected from harsh weather. This chimney vent cover cap is designed in the shape of an umbrella and made of high-quality stainless steel material.
eBay
Solid Silicone Rubber Caps 2mm to 16mm T Type Plug Cover Snap-on Gasket Blanking End Caps Seal Stopper
Aliexpress UK
HETAS CERTIFIED. TWPro is HETAS Approved and is UKCA marked. (Can only be used in conjunction with other TWPro Flue parts ). Making installing chimney systems quick and easy! TWPro twin wall insulated chimney parts are secured together by using a locking band.
eBay
5-25pcs Black Silicone Rubber Hole Caps T Type Plug Cover Snap-on Gasket Blanking End Caps Seal Stopper 2.5mm-15mm
Aliexpress UK
For ventilation ducts, chimneys and air extraction hoods. Guards provide maximum protection without compromising chimney performance. Due to the light and screen setting difference, the item's color may be slightly different from the pictures.
eBay
1PC Bathtub Shower Faucet Handle Accessories Mixing Valve Pull Brass Pull Cap Water Divider Pull Cap Handle
Aliexpress UK
For ventilation ducts, chimneys and air extraction hoods. Guards provide maximum protection without compromising chimney performance. 1 x Chimney Cap. Made of high-quality 304 stainless steel, cold and high temperature resistant, durable.
eBay
316 Stainless Steel 22mm 25mm Bimini Top Fitting Marine Hardware Slide Cap Slide Jaw Sleeve Pipe Eye End Cap
Aliexpress UK