Disclosed are substantially enantiomerically pure bis-phosphine compounds comprising a substantially enantiomerically pure chiral backbone linking two phosphine residues wherein one of the phosphine residues has three phosphorus-carbon bonds and the other phosphine residue has two phosphorus-carbon bonds and one phosphorus-nitrogen bond wherein the nitrogen is part of the chiral backbone. The sealed letter not less than a predetermined thickness is rejected in first sorting station D, and the sealed letter which is not thicker than the predetermined thickness and in which the suspected object is not detected is conveyed as it is to second sorting station G. The plunger may include a recess in a first end thereof having a seal assembly located therein and including a pin member inserted into the recess and an elastomeric sealing element molded around the pin member while inserted into the recess of the plunger. Also included are front wheels and rear wheels, and front arms and rear arms each having proximal and distal ends. The adapter sleeves include respective first and second mobile phone receiving areas for removably receiving first and second mobile phones having different configurations. The first member includes a pair of curved side walls connected to each of a front wall, an upper curved wall, and a lower curved wall, wherein a length of a first curved side wall is less than a length of each of a second curved side wall, the upper curved wall, and the lower curved wall, and wherein an edge of the second curved side wall is offset from an edge of the front wall.