What are you going to use it for? Inside the trans pan, or something else??

On my trans and oil pans, I just run a strong "rare earth" magnet on the outside of a rear facing part of the pan. It doesn't need to be inside the pan (or on the bottom) to work.

Scott B. "I'm a self-made man... I started with nothing, and I still have most of it!" 68 360 rusty B'cuda 'vert (GO Fish)13.59@ 98.72 mph 69 340 GTS stock 14.18@ 95.60 mph 01 5.9L Ram 1500 Quad Cab 4x4 01 3.5L 300M 16.23@ 86.97 mph