I have a pair of virtually 'as new' 30mm Apel mounts (rings and bases) for a Sako rifle. (These are the tapered 'Dovetail' type which will ONLY fit a Sako!)
They are 17mm from bottom of base to bottom of scope tube. They were used on a Sako 75 in 6.5 x 55 calibre and held a x50 objective scope.
They even have a windage adjustment in the rear base and come with an Allen key.
If you know anything about mounts, then you will already know that these are about as good as you can get (better than Optilocks!) and would cost you about £200 new!
They can be yours for £120 posted.
(Also advertised on the Airgun BBS)