The Bahtinov Mask Made of acrylic. And it has whole aluminium process Masks now feature 3 holes which can be attached with 3 screws to prevent the mask from falling all the way to the ground Perfect focusing for your CCD, DSLR or Webcam in seconds Light weight so you wont upset the balance on your scope (65-100mm)Suitable for telescopes front end diameter 65mm to 100mm, Universal adaptation, 3 bolts with plastic cover allow the mask to be simply attached to any telescope (85-120mm)Suitable for telescopes front end diameter 85mm to 120mm, Universal adaptation, 3 bolts with plastic cover allow the mask to be simply attached to any telescope (105-150)Suitable for telescopes front end diameter 105mm to 150mm, Universal adaptation, 3 bolts with plastic cover allow the mask to be simply attached to any telescope (150-200)Suitable for telescopes front end diameter 150mm to 200mm, Universal adaptation, 3 bolts with plastic cover allow the mask to be simply attached to any telescope. (175-220mm)Suitable for telescopes front end diameter 175mm to 220mm, Universal adaptation, 3 bolts with plastic cover allow the mask to be simply attached to any telescope Colour:black Material:plastic Size:59-83mm in diameter,Product size: 60mm Package Contents: 1*Telescope Astronomy Focusing Mask 1*boxes Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.