This 12" plastic dust cap is suitable for:
Omegon Pro Astrograph 304/1200
Omegon Advanced X N 304/1500
Omegon ProDob N 304/1500 DOB II
Omegon N 305/1500
Fitting to the tube: the cap is made of plastic. For better grip, the cap has ribs inside the rim. For an optimal fit to the tube, you can grind the ribs slightly with a file. However, please keep in mind that the cap always fits a little more tightly in winter than in spring.