Soft-sided carriers and trailers commonly use breathable mesh panels and zippered mesh doors to provide airflow. Many also include transparent or mesh front panels so the dog can see out and you can easily check on them.
Common security features include interior safety straps or leashes that clip to a harness, reinforced zippers and buckles, adjustable drawstrings or top closures, and straps or attachment points to anchor the carrier to a bike or car seat.
Portability options include foldable frames and quick-release wheels for compact storage, removable or quick-release bike-mount attachments, and padded shoulder, backpack, or crossbody straps for hands-free carrying.
Slings are intended for very small dogs (examples show small slings up to about 5 lb and medium slings around 5–10 lb). Bike baskets and small soft carriers commonly list limits of about 18 lb.
Listed capacities vary: small slings around 5 lb, many bike baskets and soft travel bags up to about 18 lb, some bike trailers up to 40 kg (≈88 lb), and larger crates or enclosures rated up to about 100 lb.
