Cardonne

Problem I find when buying any dildo or plug is that the dimensions quoted can vary quite a bit from the real size. You could try stretching your sphincter, with the smaller dildo in place, by running your finger inside your hole. When that feels nice and loose, then add another, and so on, until the new, bigger one slips in. Or, you could look for a common household item that is the size you need.

3.25 inches diameter if there is some flexability in the material, currently stretching to 3.5, but that's a hollow plastic cone that deforms to an oval shape when I squat down. (Some of you guys are doing pretty impressive stuff!)

Often have one tennis ball in place, have had two for ten minutes during the 'warm up' to a longer session. Once forgot about one ball being in place, then, went off to the gym, came back to have lunch, then went to the toilet and thought I was constipated ... until a familiar object re-appeared!