Below is a part number breakdown for the RSMF series of Metal Oxide Film resistors from Stackpole Electronics.
For the 3W power (RSMF3), you may see the -C1 suffix code added on the ordering code, such as RSMF3JA20R0-C1.
Normally the RSMF3 is taped at a class 2 (63.5mm) taping width (as the dimension “D” in the image below). The -C1 denotes class 1 (narrower) taping. It’s just packaged at an inside tape to inside tape spacing of 52.4mm instead of 63.5mm.
There is no functional implication for this suffix code.
Applicable Part Numbers
RSMF3JA100K-C1
RSMF3JA100R-C1
RSMF3JA10K0-C1
RSMF3JA10R0-C1
RSMF3JA180K-C1
RSMF3JA18K0-C1
RSMF3JA1K00-C1
RSMF3JA1K50-C1
RSMF3JA20K0-C1
RSMF3JA20R0-C1
RSMF3JA220R-C1
RSMF3JA240R-C1
RSMF3JA2K00-C1
RSMF3JA2K20-C1
RSMF3JA30K0-C1
RSMF3JA330R-C1
RSMF3JA33R0-C1
RSMF3JA3K30-C1
RSMF3JA470R-C1
RSMF3JA4K70-C1
RSMF3JA560R-C1
RSMF3JA56K0-C1
RSMF3JA56R0-C1
RSMF3JA6K80-C1
RSMF3JA820R-C1