The PEXP4-SX-4/1 is a PCI Express X1 lane convertor.
If your motherboard only has a PCI Express X1 slot, this adapter will allow you to install a PCI Express X4 in it. However your PCI Express X4 card will run at the X1 bus speed of 500 MB/s.
The height of this adapter is 1.05"and the width is 2.27"
Other combinations of lane reduction adapters are possible with slight modifications, upon request.