I enjoyed Joanna Angel's spiked duotone balls. I found them easy to insert with generous lube or by placing them in a condom. I definitely felt them. It took a few minutes to get comfortable with the string sticking out. At first it felt like they might pop out but soon I was running around my house, doing work outs and enjoying all my trips up and down stairs. The only thing I disliked was the feeling of having to pee all the time from where it presses.