Ok, so I was wrong about them having any magnetic anything holding them in place - guess mine were just stuck
However they are spring loaded.
Will post spring dimensions shortly - have a question about which microfiche shows these on TT, hopefully someone responds.
Ok - they are about a half inch long (uncompressed) 11.5mm and just under 3/8ths in. (4.5mm) wide. Wish I could be more help...