Wawa:
4" 7-segment displays have several LEDs in series per segment. Usually four.
Vf (working voltage) of four LEDs can be 8volt or more, depending on LED colour.
Easy to drive them with a TPIC shift register.
TPIC6B595 (ebay) if you build it yourself.
Sparkfun uses the TPIC6C596 on these boards.
Leo..
Thx Leo.
That is what I am using right now. The TPIC6C596 from sparkfun. But I keep damaging the DP (decimal point).
Could it be because of the sparkfun board is designed for their own 6.5" display 7-Segment Display - 6.5" (Red) - COM-08530 - SparkFun Electronics ?
Or maybe my 4" displays are bad quality? I have damaged 4 DPs 
Should I use bigger resistors (such as 220 ohm) between my 4" and TPIC6C596 board?
Bronson