Casio FX-991ES Scientific Calculator - Black. keys Two-way attachable Hard caseHard case that's attachable and detachable in both the directions 2 Level Authenticity CheckBefore and After purchase, with QR code feature. Scan QR code to check for authenticity. Number of Functions : 417Support Statistic Trigonometry, permutation & combination, logarithmic, integration, differential, simultaneous & polynomial equation, vector, matrix, complex numbers, Base-n calculations and many more Excellent Quality: Wear-Resistant printing, Drop-Resistant bodyThe Casio scientific calculators undergo rigorous quality tests and only those models reach the customer which deliver maximum durability Japanese Trusted QualityCasio Calculators comply with ISO 14001, and ROHS policies and abolish usage of harmful substances.