Groz-Beckert Longarm Needles are the recommended brand from Gammill. Specific MR134 needles give you strong needles that have minimal deflection and designed to be multi-directional.
Standard Size is 110/18 #4, Other common sizes are 90/14 #3 and 100/16 #3.
FFG refers to a titanium needle. SES refers to a ball point needle. Normally they are combined FFG/SES.
PLEASE NOTE: Gammill recommends a "Sharp" vs "Ball Point" for normal quilting. Look for the "R" in the bottom corner to ensure you have the correct needle.