Mary, I've read on the Janome 6500 list that they might be a teeny bit longer than Schmetz needles. I've had difficulty using them at times too.
Kathy

I have a set of Klasse needles and never experienced any problems with them

I have ordered from Nancy's Notions several times in the past year or so, and lately the orders have arrived with a gift of a Klasse sewing machine needle. Each time I have tried to use one in my machine, (Elna 6003) it starts skipping stitches. As soon as I change to a different needle, the problem stops. I know it must be the needle, because everything else - fabrics, batting, thread, machine settings - remains the same. Anyone else have the same problem? Thoughts?