A metal gauge with sliding pointer for hem and seam allowance consistency. A great time saving device. Set it to the desired length, measure and mark, and you're done.
 
Product details:
Made in United Kingdom
Weight: 0.39 oz (11 g)
Dimensions: 7.1 x 3 x 0.1 in (18 x 7.5 x 0.2 cm)