Holy Trainer - questions from potential buyers

Hello,

I am genuinely considering purchasing one of these, but the site mentions that the internal tube length is 60mm. My flaccid penis measures about 12cm from the pubic bone. Since I’m roughly average for a UK male, it’s hard to believe this device wouldn’t suit me. However, the general consensus on the website seems to be: if you get it wrong, tough luck! So any advice would be welcome.