An 'ΙΣ ΧΣ ΝΙΚΑ' (Ἰησοῦς Χριστὸς νικᾷ) christogram translates as "Jesus Christ Conquers". It is located in the four corners of the cross, which is a depiction of the 'ΙΣ ΧΣ ΝΙΚΑ' arrangement according to medieval Greek tradition.
Enamel stickers with orthodox symbols. Can be applied to any surface. For best results, preheat the sticker with a hair dryer: direct hot air at the sticker and heat it for at least a minute to soften the surface.