For Ranger School you are required to bring one 4-pack.
For Sapper Leader Course you are require to bring two 4-packs.
For SFAS you have the option to bring one 4-pack.
These are better known as "Map Markers". I recommend you bring as least two or three packs to these courses. You will use these a lot. Obviously you use these during land nav, but you also use these every time you have to produce an OPORD at Ranger and Sapper. You will also want to buy an alcohol correction pen (white) so that you can sterilize your maps after planning and before you step off. It's a good idea to take some electrical tape and tape the correction pen cap to the bottom of the multiple color marker case (see pictures: this is the one that I used during Florida Phase of Ranger School). This way you'll always have them together.