The OffGrid Extension adds 40% more capacity to your OffGrid cargo basket. Installation is easy - just plug it in, tighten it down, load it up and hit the road. At 22 inches long, it frees you to bring another cooler, a box of firewood, or a couple more duffels. Large specifications: Weight: 17.60 lbs. Dimensions: L 22.00 in x W 49.00 in x H 7.00 in. Minimum Crossbar Spread: 36 in. Maximum Crossbar Spread: 60 in. Medium Specifications: Weight: 12.50 lbs. Dimensions: L 18.00 in x W 40.00 in x H 7.00 in. Minimum Crossbar Spread: 30 in. Maximum Crossbar Spread: 38 in.