I prefer keeping my lens hoods mounted on all my lenses because I hate fumbling with hoods when I want to change lenses. I've found the following helpful to me as just the hoods alone won't prevent dust or debris off the front of the lens even in storage. This is only related to the current lenses I have but leaves a question I'd like to ask at the end of this post. 1 - Rokinon 7.5FE lens comes with a petal mounting lens cap. 2 - Olympus 9-18 takes the LH-55B hood which allows enough clearance to remove the standard lens cap without removing the hood. 3 - Olympus 12-40 takes the LH-66 hood which, as above, provides enough clearance to remove the standard lens cap. 4 - Olympus 17 f1.8 takes the LH-48B hood which takes the 62mm lens cap at the front of the hood. 5 - Olympus 40-150 (non-R) takes the LH-61D hood which takes the 72mm lens cap at the front of the hood. 6 - Olympus 60 macro has the sliding hood LH-49 so hood can be pulled back to allow access to the standard lens cap. (I hope Olympus uses this design in future lenses as it has apparently done with new PRO 40-150 f2.8). 7 - Olympus 75 takes the LH-61F which takes the 67mm lens cap at the front of the hood. This list may be helpful to others who don't like fiddling with reverse mounted hoods, a few seconds can sometimes make a world of difference. The lens not listed is on my wishlist, the Olympus 45 f1.8 which takes the LH-40B lens hood. If someone out there has this hood could you please offer any experience with which lens cap might fit the front of this hood? Thanks to all! PS, B+H has this hood (LH-40B) listed with the 58mm lens cap as an accessory, maybe they have saved me some time researching this question?