The 186mm Center-Pinch Snap-On Lens Cap for Select WonderPana Systems and Filters from FotodioX is a 186mm front lens cap with a squeeze, spring, and snap-on mechanism. It is easy to install as well as remove, and can attach to a WonderPana FreeArc XL filter holder system in order to protect the front element of a lens that any one of those systems are mounted on. Additionally, this lens cap can be used to protect a non-ultra slim FotodioX WonderPana 186mm filter mounted on a FotodioX WonderPana FreeArc XL filter holder system, with no other filter placed in front of it.