I have the model D, which has a slightly smaller funnel than the model A. It's one of the few stps that works well for me. I use it with their slingshot harness so the stp is held in peeing position at all times, making it quite easy to use. The downside of this stp is that it's pretty stiff and can be uncomfortable to pack all day in tight underwear or tight jeans. I have their updated model as well which has a powered coating, it feels a little bit softer and less tacky than their original models. I remember seeing someone selling a model A on ftmgarage sale a while ago, it may be worth checking out, so you don't spend as much money in case it doesn't work for you.