The alignment of ONE bed of central locking castors need follow below 3 options.
1: 4 pc x A
2: 2 pc x B + 2 pc x C
3: 3 pc x B + 1 pc x C
4 pc x C cannot work on ONE bed
The 2 standard size of Central lock stem is Ø32mm x 50mm and Ø28mm x 98.5mm.So now whatever you want purchase central brake casters for replacement or build new bed.Please follow above mentioned instruction.