L visa can be extended for twice, and each time is for one month.
The needed documents for L visa extension are as follows:
1.The passport with current visa
2.One two-inch photo with white background.
3.The bank book(save at lest $3000)
4.The beijing temporary residence permit

F visa extension is much more flexible. Generally, there are two kinds of ways for extension
F ---- three months extension (0/one entry)
F ----six months extension (1/2/multi entry)
The needed documents for F visa extension are as follows:
1.The passport with current visa
2.One two-inch photo
3.The temporary residence permit
For further information, please don’t hesitate to contact by following:

Frank
Mobile: +86-13466728990.
Offline: 010-52880162
MSN：frank.0601@hotmail.com
Email：frank@visa100.org

Address: Room 1001, 10th Floor, No.3 Building of "Beijing INN", ChaoYangMenNei, Dongcheng District, Beijing, P.R.C

---By Subway: Subway Line 2, ChaoYangMen station, B-exit(Southwest exit), then go Southwest for about 150 meters, you will see "Beijing INN", we are in Room 1001 (10th Floor of No.3 Building)---When you see "7-11", you find the right building.
---By Taxi or Self-driving: we are in the southwest corner of ChaoYangMen Bridge, the inner of Second Ring(Er Huan Road); our building("Beijing INN") is in the southwest corner of "Bank of China" and "ChaoYangMen SOHO".