Towa Bobbin Tension Gauge for M SizeM style Towa Bobbin Tension Gauge (TM M) is used to measure bobbin tension for longarm quilting machines. This model is for use with M style bobbins only. The TOWA bobbin tension gauge puts a numerical value to the amount of tension placed on a bobbin. This is very helpful as it allows you to quantify the amount of tension placed on a bobbin thread, so you have a benchmark to base bobbin tension. To measure the tension of your bobbin, place your