Here's what other sites are saying:
The AIRE 4in Barrel Pump packs a punch. This durable 4in-diameter pump inflates even the largest raft with ease. A typical situation: it's 80 degrees on the shore when you fill your boat with air, while the water is a rather chilly 55 degrees. Your boat is in for an embarrassing surprise--shrinkage. Bring along the AIRE 4in Barrel Pump to keep your boat drum tight and maneuverable on the water.