that the hole in the tube is larger than the largest stone in your gravel.
most hardware, farm supply, and building supply stores have an extensive selection of plastic tubing, and you only need a couple of inches, which they might just give you. if it costs more than a quarter, you need to find a friendlier store. to fit larger funnels, just stack short sections of tubing until you get down to the size needed for your bag.
if the bag has several cavities, pack the small ones first. as the sand flows into the cavity, squeeze, punch, hit, and bang on the bag to force sand into the corners.
when a 