The Cokin system has been around since 1978 and has often been considered as the most complete and versatile "system" to build into.  In principal you have a generic filter holder, which has 3 or 4 slots that will accommodate filters of different tones, colours, special effects.  

At the rear of the holder is a space to attach a threaded mount - and it’s this that then attaches to the front of your camera lens - so if you have 3 lenses all of different size threads (say 55mm, 58mm and 67mm), you then need 3 adaptors (they cost about £1-2 each) but ONLY one set of filters - a real money-saver.

The beauty is you can have one complete system and use it on lots of lenses, simply by swapping adaptors - and its not unique to a particular make or model of lens - you just need an adaptor the same filter thread as the lens you want to use it ons.

This sale contains a Cokin P121L (ND2) Filter

The filter is used but in Very good condition. 

Any handling marks will be minimal and certainly not show in any photos taken.