Our Trinity Rambler basket bag is made specifically for the classic Wald 137 basket, and it nestles perfectly inside.
The Trinity Rambler is a roll top designed bag, so it can be stuffed full, and roll down closed to protect the interior items. If you want to keep the inside closed up, but still have a little extra left over to pack, we added webbing tabs to attach a cargo net if needed. Our basket bag was also designed in mind to hold a paper grocery bag sitting straight up inside, and then the extra long front straps can help secure the contents.
A couple of extra pockets were added to the Trinity Rambler both inside and out for organization. Inside there are two smaller pockets to help organize your gear with a key clip, and one large inside pocket on the opposite side. Outside there is an ample open pocket to put extra quick access items like a cap or bandana, plus if you want your strap loops tucked in. If you do happen to shred and take your bike on some bumpy single track, some heavy items like a u-lock might try to bounce out of your outside pocket if not looped with your straps first.
Whether you're a commuter or doing some light rambling via bike our Trinity Rambler can be taken off the bike with ease and can be used with an additional shoulder strap to carry, just clip it onto the side D rings and go.
Or if you're looking to keep your basket bag there for the long haul (or running a large rack instead of basket) there are three webbing strips along the bottom to secure your bag with to zip ties(or lock) to the basket/rack.