The Sweetwater UL 43L is an ultralight pack from Big Agnes aimed at fastpacking and multi-day trekking. Running-vest-style shoulder straps hug the body closely and limit load sway during faster hiking or running, which matters for fastpacking specifically. An injection-moulded HDPE framesheet with an adjustable torso length (38–56 cm) and a ventilated foam back panel handle load transfer and airflow.
At 43 L and 1190 g, that works out to roughly 27.7 g per liter — a solid figure for a pack with a rigid framesheet rated to carry up to 13.6 kg. The main compartment closes with a top lid and drawcord, backed up by two side mesh pockets and one front mesh pocket, plus an integrated, removable rain cover. The hip belt is padded but fixed (not removable) and carries no pockets — a common trade-off in lightweight builds.
The shell is made from recycled 70D Robic nylon ripstop sourced from ocean-bound fishing nets, finished with a PFC-free DWR coating. Reservoir compatibility up to 3 L rounds it out for full-day trekking without frequent water stops.