The hold strap assists a frame to be secured, and the frame can be around a user’s neck when he/she does not use it, and it can prevent from dropping while the user moves or from a loss. The strap can be cut to any necessary length.

The shield can be mounted with a fewer actions if the shield fitter is used. The shield is set to the upper part, and if the frame linearly lowers along the groove, it can be easily mounted.