which is the best device?

Hello everyone, I’ve lately connected with a master who wants me to purchase a chastity device and send the keys over once it’s secured. I’ve been scouring the internet and have discovered plenty of options! However, since this is all new to me, I’m not sure which one is ideal. I am male, and I want something that fits when flaccid with little risk of an erection breaking through! My master has made it a challenge for me; if I pick the wrong one, I’ll be in big trouble!! Thank you for reading. Hopefully someone here can offer some advice.