diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/KmerBytesWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/KmerBytesWritable.java
new file mode 100644
index 0000000..ea951ba
--- /dev/null
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/KmerBytesWritable.java
@@ -0,0 +1,150 @@
+/*
+ * Copyright 2009-2012 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package edu.uci.ics.genomix.type;
+
+import java.io.IOException;
+import java.io.DataInput;
+import java.io.DataOutput;
+import org.apache.hadoop.io.BinaryComparable;
+import org.apache.hadoop.io.WritableComparable;
+import org.apache.hadoop.io.WritableComparator;
+
+public class KmerBytesWritable extends BinaryComparable implements WritableComparable<BinaryComparable> {
+    private static final int LENGTH_BYTES = 4;
+    private static final byte[] EMPTY_BYTES = {};
+    private byte size;
+    private byte[] bytes;
+
+    public KmerBytesWritable() {
+        this(EMPTY_BYTES);
+    }
+
+    public KmerBytesWritable(byte[] bytes) {
+        this.bytes = bytes;
+        this.size = (byte) bytes.length;
+    }
+
+    @Override
+    public byte[] getBytes() {
+        return bytes;
+    }
+
+    @Deprecated
+    public byte[] get() {
+        return getBytes();
+    }
+
+    @Override
+    public int getLength() {
+        return (int) size;
+    }
+
+    @Deprecated
+    public int getSize() {
+        return getLength();
+    }
+
+    public void setSize(byte size) {
+        if ((int) size > getCapacity()) {
+            setCapacity((byte) (size * 3 / 2));
+        }
+        this.size = size;
+    }
+
+    public int getCapacity() {
+        return bytes.length;
+    }
+
+    public void setCapacity(byte new_cap) {
+        if (new_cap != getCapacity()) {
+            byte[] new_data = new byte[new_cap];
+            if (new_cap < size) {
+                size = new_cap;
+            }
+            if (size != 0) {
+                System.arraycopy(bytes, 0, new_data, 0, size);
+            }
+            bytes = new_data;
+        }
+    }
+
+    public void set(KmerBytesWritable newData) {
+        set(newData.bytes, (byte) 0, newData.size);
+    }
+
+    public void set(byte[] newData, byte offset, byte length) {
+        setSize((byte) 0);
+        setSize(length);
+        System.arraycopy(newData, offset, bytes, 0, size);
+    }
+
+    public void readFields(DataInput in) throws IOException {
+        setSize((byte) 0); // clear the old data
+        setSize(in.readByte());
+        in.readFully(bytes, 0, size);
+    }
+
+    @Override
+    public void write(DataOutput out) throws IOException {
+        out.writeByte(size);
+        out.write(bytes, 0, size);
+    }
+
+    @Override
+    public int hashCode() {
+        return super.hashCode();
+    }
+
+    @Override
+    public boolean equals(Object right_obj) {
+        if (right_obj instanceof KmerBytesWritable)
+            return super.equals(right_obj);
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        StringBuffer sb = new StringBuffer(3 * size);
+        for (int idx = 0; idx < (int) size; idx++) {
+            // if not the first, put a blank separator in
+            if (idx != 0) {
+                sb.append(' ');
+            }
+            String num = Integer.toHexString(0xff & bytes[idx]);
+            // if it is only one digit, add a leading 0.
+            if (num.length() < 2) {
+                sb.append('0');
+            }
+            sb.append(num);
+        }
+        return sb.toString();
+    }
+
+    public static class Comparator extends WritableComparator {
+        public Comparator() {
+            super(KmerBytesWritable.class);
+        }
+
+        public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {
+            return compareBytes(b1, s1 + LENGTH_BYTES, l1 - LENGTH_BYTES, b2, s2 + LENGTH_BYTES, l2 - LENGTH_BYTES);
+        }
+    }
+
+    static { // register this comparator
+        WritableComparator.define(KmerBytesWritable.class, new Comparator());
+    }
+
+}
+