SV188 has a reflectivity of 90%, while the SV188P has a reflectivity of 99%. SVBONY SV188P 1.25-Inch 90 Degree Dielectric Mirror Diagonal 99% Reflectivity Dielectric Coatings w/ Brass Compression Rings Features ： 1. SV188P features sophisticated, Multi-layered dielectric coatings that provide an astounding 99% reflectivity for maximum view brightness and sharpness. 2. Dielectric mirror coatings are more durable and more reflective than enhanced aluminum coatings 3. Brass lockScrew for eyepiece or adapter and brass Compression rings features more precision and prevent barrels or the surface of eyepieces from marring and scratching. 4. 1.25" nosepiece barrel is threaded to accept 1.25-Inch eyepiece and filters 5. Diagonal provides a comfortable 90-degree viewing orientation when observing the night sky through a refractor, Maksutov-Cassegrain (Mak-Cass) or Schmidt-Cassegrain telescope 6. Machined and anodized aluminum housing features machine-threaded baffles for optimized contrast Specifications : 1. Brand: SVBONY 2. Model: SV188P 3. Size: 1.25-Inch 4. Coatings : Dielectric 5. Reflectivity: 99% 6. Thread: 28.5*0.6 7. Material: Aluminum Alloy 8. M4 Set Screws 9. Net Weight: 125g / 4.41oz

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