Follow up to Jason's post, this picture shows the relative size of the Hyperflow and my old Pur filter.
I weighed everything you see in the picture. The MSR unit came to 248 grams (8.8 oz), the Pur came to 349 grams (12.3 oz) or about 101 gram (3.5 oz) difference. The cap, however, weighs 36 grams (1.3 oz). Since it would presumably replace the cap on a water bottle, the scales would tip slightly further toward the MSR unit.
If you use a bladder, you can eliminate the caps and set either filter to pump directly into the bladder. The Pur bottle stopper weighs 24 grams (0.8 oz) and the effluent hose 34 grams (1.2 oz).