These holders are the same as our 2256 and 2257 with one difference. Our 2256 and 2257 use a DPMT insert which has an 11° relief angle. These holders use a DCMT insert which has a 7° relief angle. As with many insert holders and inserts, they change over time. The original DPMT insert that we use with the 2256 and 2257 holders has become less available, and offers less choices for various different chip breaker designs. The DCMT insert is readily available with a wide selection of different insert styles. Note: Our customers who have been cutting brass have found that our uncoated DPMT (11°) insert (with the straight groove chip breaker) works very well and gives them an excellent finish. These inserts are no longer available. This is why we have added our new holders with a 7° relief angle. Uncoated DCMT (7°) inserts with the preferred chip breaker are available. The coated inserts with different chip breaker designs are still available in both the DPMT and DCMT inserts.