What are the advantages of the SF11 penta prism?
High refractive index → Enables a more compact prism size (thinner than BK7 for the same optical path folding).
High dispersion → Suitable for dispersion-sensitive systems (as a compensation component in spectrometers).
Short wavelength cutoff → Transmission drops sharply below 380nm, making it unsuitable for deep ultraviolet applications.

Comparison of SF11 penta prism, BK7 (K9) penta prism and fused silica penta prism
Properties	SF11 Penta Prism	BK7(K9) Penta Prism	Fused Silica Penta Prism
Refractive Index	1.7847 (higher)	1.5168 (moderate)	1.4585 (lower)
Dispersion	Higher (25.76)	Moderate (64.17)	Lower (67.8)
UV Performance	Poor (absorption at <380nm)	General (absorption at <350nm)	Excellent (starting from 185nm)
Size Advantage	The most compact (high refractive index)	Moderate	Larger (low refractive index)
Cost	Higher (special glass)	Low (conventional materials)	Highest